A capsule endoscope 10 includes an image pickup device 13, a memory 15 configured to store brightness information acquired by the image pickup device 13, and a control section 16 configured to perform control so as to compare the brightness information acquired by the image pickup device 13 with brightness information acquired by the image pickup device 13 immediately before acquiring the brightness information and stored in the memory 15, further acquire, when the comparison result falls within a predetermined threshold, brightness information through the image pickup device 13, further compare the acquired brightness information with the brightness information acquired by the image pickup device 13 immediately before and stored in the memory 15, and on the other hand, when the comparison result is greater than the predetermined threshold, pick up an image through the image pickup device 13 and store the picked-up image in the memory 15 or transmit the picked-up image to outside the capsule endoscope 10 through an image transmitting section 14 provided in the capsule endoscope 10.
