To suppress the generation of metallic powder and the occurrence of a flaw and metallic pollution, in a double side polisher to polish the both faces of, for example, a semiconductor substrate.

Tooth parts of an internal tooth gear 1 and a solar gear engaged with the outer peripheral tooth G of a carrier C to hold a semiconductor substrate consist of a plurality of pins 5,... disposed at given pitches and sleeves 6,... rotatably fitted in the pins 5,.... The sleeves 6,... are coated resin or the surface of the sleeve made of a metal is coated with resin, when the sleeve is made of resin, resin having excellent wear resistance and mechanical strength and a low friction factor is used. By using a so formed double side polisher, a work is polished.