To provide a method of manufacturing a toothed belt in which a belt back surface can be molded in a desired form suitable for carrying articles simultaneously as a toothed belt main body is molded.

On one surface side of an endless molding guide belt 30 which is rotated in the same direction as a molding wheel 20, a carrying surface forming die by recessed holes 32 is provided. As a part of the molding guide belt 30 in an arc form larger than the flange diameter of the molding wheel 20 by a specified size is faced at a part of a tooth line of the molding wheel 20, a die cavity 25 which the carrying surface forming die 32 face is formed in a gap between teeth, fused resin 27 is injected there from an injection nozzle 26 on the starting end side, and a toothed belt 29 is released from the final end side of the die cavity 25 to be extrusion-molded. In the molded toothed belt 29, a carrying surface by protruded parts 29c suitable for carrying articles are simultaneously formed on a belt back surface.