A capsule endoscope includes a sensor, an analyzer, a counter, a signal generator, and an imager. A count value becomes a reference value when an imaging synchronization signal is generated. When the count value changes from the reference value to a first predetermined value, the signal generator generates the imaging synchronization signal. A second time that is necessary for the count value to change from the reference value to the first predetermined value is fixed or variable. The second time is longer than a first time in a case in which the second times is fixed. A maximum value of the second time is longer than the first time in a case in which the second time is variable.