An ion flow modulator with high reliability used in a photocopying machine to obtain a high quality image. The ion flow modulator includes an insulating substrate, a common electrode formed on one major surface of the insulating substrate, a plurality of ion flow control electrodes formed on the other major surface of the insulating substrate, a photoconductive layer formed on the insulating substrate and connected to one end of each of the ion flow control electrodes, a first voltage application electrode formed on the insulating substrate and connected to the photoconductive layer, a resistance layer formed on the insulating substrate and connected to the other end of each of the ion flow control electrodes so as to interpose the ion flow control electrodes between the photoconductive layer and the resistance layer, a second voltage application electrode formed on the insulating substrate and connected to the resistance layer, and a DC power source for applying voltages having opposing polarities to the first and second voltage application electrodes. The ion flow passage holes are formed through the insulating substrate and the common electrode. A means is provided for generating ions to pass through the ion flow passage holes.