PURPOSE: To prevent a reinforced fiber from breaking, by a method wherein a large cylinder for measurement is arranged on a position separated from a screw fitting position, an injection plunger which is fitted into the large cylinder is made into a hollow plunger having a through hole, the inside of which is made a flow path for raw materials and the flow path is made interruptible between the hollow plunger and a screw.

CONSTITUTION: Molding raw materials comprised of plastic and a reinforced fiber is pressed into a small cylinder 6 from a pressing-in cylinder 18 by a pressing-in piston 20, the plastic is molten with a rotation of a screw 8 in the small cylinder 8 and the molding raw materials are kneaded. The molding raw materials are fed to the hollow plunger 4 connecting with the small cylinder 6 and measured and sent into a large cylinder 2 which is fitted over the hollow plunger 4. The hollow plunger 4 is moved in the direction where measure capacity is increased with this measurement action, after completion of the measurement, a rotation of the screw 8 is suspended and the screw 8 is brought into contact with the hollow plunger 4, through which raw material flow path is interrupted.