To provide an ultrasonic capsule endoscope which has a simple constitution and can perform ultrasonic observation by inflating a balloon provided in a deflated condition in the ultrasonic capsule endoscope at the time of ultrasonic observation.

In the ultrasonic capsule endoscope 1, an ultrasonic transducer section 6 which transmits and receives ultrasonic waves is included, and the balloon 5 which is inflated and changed by the pouring of an ultrasonic transmission medium 13 is provided in the deflated condition at a predetermined position on the outer peripheral face of a capsule. A storing bag 12 which stores the ultrasonic transmission medium 13 poured into the balloon 5, and a high molecular absorbent 11 which is an ultrasonic transmission medium moving means supplying the ultrasonic transmission medium 13 stored in the storing bag 12 to the inside of the balloon 5 through a fluid aperture 2d provided in the capsule, are formed within the capsule.