Power transmitting apparatus and contactless power transmission system

System that transmits power to the power receiving device 50 from the power transmitting device 10 by using electromagnetic induction between the power receiving coil 60 and the power transmission coil 40. Power transmission device 10 includes a power switching circuit 14, a first capacitor 20, a power extraction circuit 30. Power switching circuit 14, and an output point P and the switching element 16, by a predetermined change of the potential at the output point P by switching the switching element 16 at a predetermined switching frequency f. The predetermined variation is a potential variation as obtained by half-wave rectifying a sine wave variation having a predetermined amplitude. The first capacitor 20 is connected between the output point P and the first fixed potential (ground). Power extraction circuit 30 includes a power transmission coil 40 is configured to generate an alternating changes included in a predetermined variation across the power transmission coil 40. The power extraction circuit 30 is connected between the output point P and the second fixed potential (ground).