A capsule endoscope includes an image pickup device, a memory configured to store brightness information acquired by the image pickup device, and a control section configured to perform control to compare the brightness information acquired by the image pickup device with brightness information acquired by the image pickup device immediately before acquiring the brightness information and stored in the memory, cause the image pickup device to acquire brightness information when the comparison result is no greater than a threshold, compare the acquired brightness information with the brightness information acquired by the image pickup device immediately before and stored in the memory, and cause the image pickup device to pick up an image when the comparison result is greater than the threshold and cause the memory to store the picked-up image or cause an image transmitting section provided in the capsule endoscope to transmit the image to outside the capsule endoscope.
