To provide a toothed belt having a back part with reduced friction coefficient to reduce friction coefficient between the back part and an idler pulley or between the back part and a tensioner pulley and thereby to prevent wear and damage of a belt side face.

The toothed belt 1 comprises: a plurality of tooth parts 2 arranged along a longitudinal direction at predetermined intervals; the back part 4 continuous with the tooth parts 2; a core wire 3 buried in the back part 4; and a tooth cloth covering the surfaces of the tooth parts 2. Woven cloths 6 coated with rubber are laminated on the back part 4. The back face 7 is a polished face from which the woven cloths 6 are exposed. The belt has the fixed thickness.