A power transmitting belt manufacture wherein belts are molded to have various cross sections. The belts are machined to a desired cross section. Each belt is entrained about drive and driven pulleys to run the belt under a preselected tension. At least one roller is caused to engage the back surface of the driven belt to reinforce the otherwise unsupported belt at the point of cutting between drive and driven pulleys. A pair of opposed cutting blades are engaged with the opposite sides of the belt to form the opposite side edges of the final belt section. An apparatus is disclosed for fabricating such a power transmitting belt which has a belt feeder for placing the belt over a drive pulley and a driven pulley, a pair of belt machining units each having at least one rotatable cutting blade for cutting the side walls of the belt, X-axis movable bases for controlling the movement of belt machining units towards and away from each other and thereby control belt width, a roller unit, and a Y-axis movable base for carrying the roller unit for pressing a roller of the roller unit against the back surface of the belt.