A capsule-type endoscope 20 that has a CCD 23 arranged at an end portion in a longitudinal direction and a power receiving coil 21 that receives an electric power by means of a change in a magnetic field in the longitudinal direction has a structure that enables the capsule-type endoscope 20 to float with a longitudinal direction thereof being perpendicular to a surface of water 31 that is retained inside a stomach 30A. A wireless power supply apparatus 10 has three sets of coils 44 to 46 that are arranged on an individual to be examined 39 and that generate a magnetic field in directions that are orthogonal to each other, a gravity sensor 16 that is arranged on the individual to be examined 39 and that detects a gravitational direction, a coil selection section 51 that selects a coil that generates a magnetic field in a gravitational direction that is detected by the gravity sensor 16, and a drive section 41 that applies a current to the coil that the coil selection section selects.
