The present invention is to provide a capsule endoscope capable of making an appropriate observation without being disturbed by such as reflections from a surface of liquid and folds, when making an observation in a body cavity while floating in the liquid introduced into a subject. A center of gravity is set using a weight (8) at a position decentered at which a capsule casing (3) is stabilized in liquid (9) introduced into a subject (2) without rotating except for rotation about an axis in a direction of the center of gravity, and an in-vivo image in the body cavity is taken using an imager (4) whose imaging field is set such that a surface (9a) of the liquid is out of view when the capsule casing (3) floats in the posture described above. An example of the imager (4) is imaging optical systems (4a) and (4b) whose optical axes are inclined with respect to a longitudinal axis of the capsule casing (3).
