A charging device of the present invention includes a charge roller adjoining
or
contacting the surface of a photoconductive element. A DC and an AC voltage source
output a DC and an AC voltage, respectively. A voltage applying device superposes
the DC and AC voltage and applies the resulting superposed voltage to the charge
roller. A waveform controller causes the AC voltage source to generate an AC voltage
having the waveform pattern of particular noise and frequency lying in a preselected range.
