A rotary non-contact connector and a non-rotary non-contact connector enable data transmission in a non-contact mode by radio transmitters-receivers by combining rotary transformers or stationary transformers and radio transmitters-receivers, and providing power systems with buffer functions by a storage means to receive supplied electric power. Each of the rotary non-contact connector and the non-rotary non-contact connector has first and second radio transmitters-receivers provided between a rotor and an annular stator of a rotary transformer and between first and second stationary members of a stationary transformer to permit two-way radio data communication in a non-contact mode. Furthermore, storage means are provided to implement a buffering function for a power system.