PURPOSE: To enable power transmission to be performed with no contact, by making the power transmission between a rotor part and stator part by the use of a rotary transformer which is equipped with coils facing the rotor part and stator part.

CONSTITUTION: A power-supply circuit 4 is installed inside a rotor part 1, and power is supplied from the power-supply circuit 4, through a rotary transformer 3, to a load device 5 which is loaded at the stator part 2. A transmitting coil 6 and receiving coil 7 of the rotary transformer 3 are coaxially situated, with a spin axis 8 serving as the center, and the transmitting coil 6 is turned facing the receiving coil. Induced voltage appears at the receiving coil 7, according to the winding ratio to the transmitting coil 6. Hence, power transmission between the rotor part and stator part can be realized without contact.