To transmit and receive plural signals between a rotating body and a fixed body, without being influenced by the rotation operation of the rotating body and to keep phases of plural signals fixed at the time of transmission/ reception of signals.

A filter plexer 27 installed on the side of a rotating body 1 and a filter plexer 28 installed on the side of a fixed body 2 are connected by a rotary joint 30, having a coaxial line 29 through which one signal can be transmitted in two directions, and an IF signal and LO signal different by frequency bands are subjected to frequency multiplexing into one signal by the filter plexer 27 and pass the coaxial line 29 of the rotary joint 30, and this frequency multiplexed signal passing the coaxial line 29 of the rotary joint 30 is demultiplexed to the ID signal and the LO signal by the filter plexer 28.