A capsule endoscope swallowable in a body (10) is provided, and includes an image pickup device (34) for picking up an image (113, 114) in the body. A transmitter (55) externally transmits information of the image. By use of an acceleration sensor (59), a capsule moving speed is detected in the body. A CPU (50) as pixel number changer changes a pixel number (Pmax, Pmid, Plow) of the image, namely resolution of the image according to information (V, L, ”L, SI) of the capsule moving speed. The CPU sets the pixel number lower according to lowness of the capsule moving speed (V). Also, the CPU sets the pixel number lower according to lowness of a capsule moving distance (L, ”L), and/or according to highness of similarity degree (SI) between plural consecutive images. Preferably, the CPU sets the pixel number by at least one of pixel binning, pixel thinning and pixel averaging.
