A capsule endoscope includes: an imaging unit configured to capture inside of a subject and to generate an image of the inside of the subject; a brightness distribution measurement unit configured to measure a brightness distribution in the image generated by the imaging unit; and an imaging controller configured to switch a frame rate of the imaging unit to a frame rate higher than a reference frame rate when an area having brightness lower than a predetermined value is distributed at a center of the image in the brightness distribution measured by the brightness distribution measurement unit and to switch the frame rate of the imaging unit to a frame rate lower than the reference frame rate when the area having the brightness lower than the predetermined value is distributed outside the center of the image.