A capsule endoscope includes: an in vivo information acquiring section that acquires information on an inside of a body of a subject; a battery that supplies power; a power source switch that turns on/off power supply from the battery to the in vivo information acquiring section; a detection section that includes at least two electrodes disposed on an outer face of a casing, and, upon detection of introduction to the inside of the body of the subject based on a change in electric resistance between the electrodes, outputs a detection signal; and a control section that controls the power source switch according to the detection signal.