PURPOSE: To pack raw material effectively by a method in which while chambers are connected to a sucking and exhausting blower, the valve mechanism stopping intermittently the communication between the sucking and exhausting blower and the chambers, is provided, whereby raw material is sucked by the pulsating sucking flow generated by the sucking and exhausting blower.

CONSTITUTION: A raw material feeding machine 11 is driven in the state of a mold being clamped, and raw material is fed into a cavity 3 by a raw material feeder 8. On one hand, a valve mechanism is intermittently operated, while a sucking and exhausting blower 16 is continuously driver. If the communication between the sucking and exhausting blower 15 and chambers 2a, 2b is intermittently stopped, pulsating sucking flow continuously acts on a cavity 3 through the sucking narrow hole 21 of the mold 1 in the chambers 2a, 2b. The more impacted in the mold, the stronger acts this pulsating sucking flow in comparison with continuously sucking flow, even when the sucking and exhausting blower 15 with same properties is used. Consequently, the sucking operation in the cavity 3 is remarkably heightened, and the raw material is effectively packed.