PURPOSE: To improve the reuse efficiency of developer by separating and removing only paper powder by making use of difference on the particle diameter and the polarity of the charge of toner, carrier, and the paper powder in the used developer.

CONSTITUTION: The toner and the carrier in discharged developer are electrostatically charged to reverse polarity each other. The paper powder is electrostatically charged to the polarity opposite to that of the carrier, and adheres to the surface of the carrier. The toner and the paper powder in the discharged developer are carried by a carrying roller R1 incorporating a magnet roll 15, and carried to a position opposed to the carrying roller R2 while adhering to the carrier. The negatively electrostatically charged carrier is carried to the opposed position, and flies to the carrying roller R2 from the carrying roller R1. On the other hand, since the positively electrostatically charged toner and paper powder receive electric force in an opposite direction, they do not fly but are separated from the carrier; and remain on the carrying roller R1. Since the toner and the paper powder remaining on the carrying roller R1 do not have magnetism, they fall to be sifted by a mesh 22, and the paper powder having large particle diameter remains on the mesh 22.