A contactless power supplying device is provided. A primary coil and a basic power supplying unit circuit are arranged in a power supplying area. The primary coil supplies secondary power through electromagnetic induction to a secondary coil of a power receiving device in the power supplying area. The basic power supplying unit circuit excites the primary coil in the power supplying area. The basic power supplying unit circuit transmits an oscillation signal from the power supplying area to the power receiving device, receives a modulated wave signal from the power receiving device that detects a modulation wave that is in accordance with a magnetic flux change, and detects the modulated wave signal to demodulate the modulation wave. A system control unit determines whether or not a metal foreign object is present in the power supplying area corresponding to the basic power supplying unit circuit based on the modulation wave.