PURPOSE: To control the amount of electrostatic charge of a brush without contacting and to perform excellent cleaning by arranging a electric field curtain sheet which is applied with alternating currents containing superposed direct current closely to part of the outer circumference of brush roll.

CONSTITUTION: The electric field curtain sheets 6 and 6' are arranged at the outer circumferences of the brush rolls 5 and 5' at intervals of about 4mm, and ≥3.5kV alternating voltage is impressed to an exposed electrode group 15 on its surface dielectric layer 18 and embedded electrode groups 16 and 17 on a substrate 20 to generate positive and negative ions; and a DC bias is superposed thereupon to adjust the voltage, controlling the amount of positive and negative ions. Toner electrostatically charged positively by a corotron 14 is removed by the roll 5 electrostatically charged negatively and toner which is not inverted to the positive polarity is removed by the positive roll 5'. Consequently, the amount of the electrostatic charge is controlled without rubbing the brush against an electrostatically charged metal and the residual toner is cleaned completely.