Disclosed is a resonant type transmission power supply device including a transmission power state detecting circuit 11 to detect a transmission power state of a transmission antenna 2, a foreign object detecting circuit 124 to detect the presence or absence of a foreign object in an electromagnetic field generated from the transmission antenna 2 on the basis of a detection result acquired by the transmission power state detecting circuit 11, and a power control circuit 125 to reduce or stop the supply of electric power to the transmission antenna 2 when foreign object is detected by the foreign object detecting circuit 124.