To improve the removability to excess material which can not sufficiently remove only a system setting an air-blowing device at a position faced to the mold surface of a cavity and a parting surface of a die.

The air-blowing device 4 is integrally arranged at the back surface side of the die 1. At the ordinary time, a spouting hole 17 is closed with a valve part 4. At the time of supplying the air-blow into the air-blowing device 4, the valve part 46 is shifted to the arrow mark direction X2 and the spouting hole 17 is opened and the air-blow is passed through a passage in the die 1 and supplied toward the cavity 10 from the back surface side of the cavity 10.