To provide a manufacturing method of canvass cloth for transmission belt where a manufacturing time of a cylindrical belt canvass cloth is remarkably shortened and a manufacturing method of a transmission belt.

A pair of canvass cloth consisting of wefts 2a positioned parallel to a longitudinal direction and warps 2b arranged at a cross angle with the weft of 90° or an angle exceeding 90° are prepared. A pair of the canvass clothes 1 are joined together with the end parts thereof trued up to manufacture cylindrical canvass cloth 4. Thereafter, the cylindrical canvass cloth 4 is spirally cut to manufacture opening canvass cloth where the wefts 2a and the warps 2b are arranged at an equal angle to each other with a longitudinal shaft. Thereafter, the opening canvass cloth is cut to given length, and the cut end parts of the canvass cloth are joined together to form belt canvass cloth in a cylindrical shape.