PURPOSE: To realize a copying device for uniformly imparting high-frequency oscillating energy to an image forming plane for electrophotographic use.

CONSTITUTION: This electrophotographic device has an image forming member provided with an electrification holding plane driven along a circulating-type path through a processing part. A resonator 100 suitable for producing oscillating energy is arranged in serially contact with the back side of a non- rigidity member so as to improve the mechanical release of toner from a surface at any one of the processing part, and oscillating energy is uniformly imparted to the non-rigidity member. The resonator 100 includes a supporting member 154, a horn 152, and a plurality of oscillation producing elements 150 driving the horn 152 and imparting the oscillating energy to a belt 10. The elements 150 are driven by a voltage signal selected by exciting a horn segmentation to a maximum top speed.