To provide a polishing device for a toothed belt without dispersion of a polishing amount between belts and within a single belt, to fix a thickness of the toothed belt after it is polished.

In a polishing device for a toothed belt formed by providing a support part A supporting a belt cylindrical unit 1 successively provided with many sleeves after cutting or belts after cutting in the belt width direction by at least two shafts, drive part B rotating the belt cylindrical unit 1 and a grinding wheel C polishing the belt cylindrical unit 1, of the support part, a roller 2 on a drive shaft side has a plurality of tooth grooves 3 extended in the lengthwise direction, a pulley is provided with a belt moving stopper part having a tooth groove work part engaged with a tooth part 18 of the belt cylindrical unit 1 and a step difference surface into contact with an end face of the belt cylindrical unit 1 to be adjacent to the tooth groove work part.