An injection molding machine comprising a processing pin provided in a fixed mold side is provided. A movable member is arranged in a space between the fixed mold and a fixed plate, the processing pin can be moved forward and backward together with the movable member with rear end portion thereof fixed to the movable member. An end portion of the processing pin is inserted into a mold plate so that it can go in and out of a gate or a cavity by the forward and backward movement of the movable member moved by a drive unit. The above construction can eliminate positional limitation due to a position of a projecting pin in a conventional injection molding machine.