diff --git a/ykoiso/src/A066_Work.java b/ykoiso/src/A066_Work.java
new file mode 100644
index 0000000000000000000000000000000000000000..f132d9e4135f37cdf98e761c0ed699b44230dedc
--- /dev/null
+++ b/ykoiso/src/A066_Work.java
@@ -0,0 +1,101 @@
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Scanner;
+
+public class A066_Work {
+    static final int END = 0;
+
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+        // 仕事の開始日と終了日
+        Map<Integer, Integer> taskScheduleMap = new HashMap<>();
+        // 各仕事の開始日
+        List<Integer> startDayList = new ArrayList<>();
+        // 仕事の数
+        final int taskNum = scan.nextInt();
+        for (int i = 0; i < taskNum; i++) {
+            int startDay = scan.nextInt();
+            int endDay = scan.nextInt();
+            taskScheduleMap.put(startDay, endDay);
+            startDayList.add(startDay);
+        }
+        A066_Work work = new A066_Work();
+        TaskDays taskDays = work.new TaskDays(startDayList, taskScheduleMap);
+        taskDays.makeConsecutiveDays();
+        System.out.println(taskDays.getMostLongWorkDays());
+        scan.close();
+    }
+
+
+    class TaskDays {
+        private List<Integer> startDayList;
+        private Map<Integer, Integer> taskScheduleMap;
+        // 最大連勤日数
+        private int mostLongWorkDays = 0;
+
+        // コンストラクタ
+        TaskDays(final List<Integer> startDayList, final Map<Integer, Integer> taskScheduleMap) {
+            this.startDayList = startDayList;
+            this.taskScheduleMap = taskScheduleMap;
+        }
+
+        // 出力用
+        public int getMostLongWorkDays() {
+            return mostLongWorkDays;
+        }
+
+        // 全てのタスクから最大連勤日数を計算する
+        public void makeConsecutiveDays() {
+            int startDay = 0, endDay = 0;
+            // 計算していない仕事が0になるまで
+            while (startDayList.size() > 0) {
+                // 開始日、終了日をリストの最初の仕事で設定
+                startDay = startDayList.get(0);
+                endDay = taskScheduleMap.get(startDay);
+                // リストの最初の仕事を計算済みにする
+                startDayList.set(0, END);
+                // 連勤の計算
+                calcConsecutiveDays(startDay, endDay);
+                // 計算済みの仕事を仕事リストから消去
+                for (int i = startDayList.size() - 1; i >= 0; i--) {
+                    if (startDayList.get(i) == END) {
+                        startDayList.remove(i);
+                    }
+                }
+
+            }
+        }
+
+        // 指定タスクの連勤計算
+        public void calcConsecutiveDays(int startDay, int endDay) {
+            int nextStartDay = 0, nextEndDay = 0, workDays = 0;
+            for (int i = 1; i < startDayList.size(); i++) {
+                // 次の仕事の日程を読み込み
+                nextStartDay = startDayList.get(i);
+                nextEndDay = taskScheduleMap.get(nextStartDay);
+                // 連勤日数がつながっている場合
+                if ((nextStartDay <= endDay + 1 && nextStartDay >= startDay - 1)
+                        || (nextEndDay >= startDay - 1 && nextEndDay <= endDay + 1)) {
+                    // 開始日と終了日を延ばせる場合更新
+                    if (startDayList.get(i) <= startDay) {
+                        startDay = startDayList.get(i);
+                    }
+                    if (nextEndDay >= endDay) {
+                        endDay = nextEndDay;
+                    }
+                    // 仕事を計算済みにする
+                    startDayList.set(i, END);
+                }
+            }
+            // 連勤日数の計算
+            workDays = endDay - startDay + 1;
+            if (workDays > mostLongWorkDays) {
+                mostLongWorkDays = workDays;
+            }
+        }
+
+    }
+}
+
diff --git a/ykoiso/test/A066_WorkTest.java b/ykoiso/test/A066_WorkTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..58f227ad466a1ed2becf646757544e0f61f98a81
--- /dev/null
+++ b/ykoiso/test/A066_WorkTest.java
@@ -0,0 +1,84 @@
+import static org.junit.Assert.assertThat;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.*;
+
+public class A066_WorkTest {
+    A066_Work work = new A066_Work();
+    A066_Work.TaskDays sut;
+    List<Integer> startDayList;
+    Map<Integer, Integer> taskScheduleMap;
+
+    @Before
+    public void setUp() throws Exception {
+        taskScheduleMap = new HashMap<>();
+        startDayList = new ArrayList<>();
+        taskScheduleMap.clear();
+        startDayList.clear();
+    }
+
+    @Test
+    public void 連勤であることを判断できる() {
+        startDayList.add(5);
+        startDayList.add(13);
+        taskScheduleMap.put(5, 12);
+        taskScheduleMap.put(13, 15);
+        System.out.println(startDayList);
+        System.out.println(taskScheduleMap);
+        sut = work.new TaskDays(startDayList, taskScheduleMap);
+        sut.makeConsecutiveDays();
+        int actual = sut.getMostLongWorkDays();
+        int expected = 15 - 5 + 1;
+        assertThat(actual, is(expected));
+    }
+
+    @Test
+    public void 連勤でないことを判断できる() {
+        startDayList.add(5);
+        startDayList.add(13);
+        taskScheduleMap.put(5, 11);
+        taskScheduleMap.put(13, 15);
+        sut = work.new TaskDays(startDayList, taskScheduleMap);
+        sut.makeConsecutiveDays();
+        int actual = sut.getMostLongWorkDays();
+        int expected = 11 - 5 + 1;
+        assertThat(actual, is(expected));
+    }
+
+    @Test
+    public void 期間がかぶっている連勤を判断できる() {
+        startDayList.add(5);
+        startDayList.add(6);
+        taskScheduleMap.put(6, 8);
+        taskScheduleMap.put(5, 12);
+        System.out.println(startDayList);
+        System.out.println(taskScheduleMap);
+        sut = work.new TaskDays(startDayList, taskScheduleMap);
+        sut.makeConsecutiveDays();
+        int actual = sut.getMostLongWorkDays();
+        int expected = 12 - 5 + 1;
+        assertThat(actual, is(expected));
+    }
+
+    @Test
+    public void タスクが3つ以上の連勤を判断できる() {
+        startDayList.add(5);
+        startDayList.add(13);
+        startDayList.add(1);
+        taskScheduleMap.put(1, 8);
+        taskScheduleMap.put(5, 12);
+        taskScheduleMap.put(13, 15);
+        System.out.println(startDayList);
+        System.out.println(taskScheduleMap);
+        sut = work.new TaskDays(startDayList, taskScheduleMap);
+        sut.makeConsecutiveDays();
+        int actual = sut.getMostLongWorkDays();
+        int expected = 15 - 1 + 1;
+        assertThat(actual, is(expected));
+    }
+}