A processing apparatus with a novel structure where a tool side rotates in relation to a main body side, capable of producing excellent quality transmission of an electrical signal from the tool side to the main body side with a simpler and more compact composition, and capable of driving an ultrasonic transducer provided on the tool side more effectively. A pair of signal coils are disposed between the main body side and the tool side so as to be able to transmit an electrical signal, and a power supply frequency to the ultrasonic transducer provided to the tool side is controlled by a power supply control member. At least one of the signal coils is provided with a coil winding path that reduces noise electromotive force generated due to an effect from power coils provided to the main body side and the tool side.