To provide a non-contact power transmission device applicable to the non-contact power transmission device and the like only using a system selected on request out of a plurality of power supply systems, and to provide a joint auxiliary device.

The non-contact power transmission device S includes a body casing 80 in which a controller 60 is housed to control a power supply operation, a plurality of power supply housings 31 fixedly mounted to the outside of the body casing 80, and used to house a power supply head 37 connected to the controller through a cable 75 to supply power by means of a non-contact electromagnetic action, and a plurality of power receiving housings 32 detachably mounted to correspond to each of the power supply housings 31, and used to house a power receiving head 47 oppositely disposed coaxially to the power-supplying head 37 to receive the power by means of the non-contact electromagnetic action. The controller 60 determines whether the power receiving head 47 can receive the power, and power supply is stopped when it is determined that it is impossible for the power receiving head 47 to receive the power.