A capsule endoscope is provided with an image pickup section having a CCD image sensor, a plurality of LEDs for emitting illumination light, a control circuit for controlling the image pickup section and the LEDs, a transmitting/receiving circuit for transmitting an image signal as a radio signal, and a battery for supplying electric power to each part of the capsule endoscope inside of a capsule case. When the capsule endoscope reaches a large intestine which is a lower digestive tract, the transmitting/receiving circuit receives an image capture initiation signal from an external transmitter provided outside of the body. The control circuit then activates the LEDs and the image pickup section to perform the image capturing at a predetermined interval.