To provide a device for supplying materials of an injection molding machine wherein its driving means such as a motor can be made into a small size and cutting at high accuracy is possible.

A groove 28 is formed by slotting in a piston 27 reciprocating by a driving means 29, and a molding material in an introducing channel 22 is scooped by the groove 28 and discharged into a blow-down channel 23. Cutting at high accuracy can be realized because an amount of cutting can be determined by a product of volume of the groove and the reciprocating cycles of the piston. When the groove is formed in a spoon shape, clogging of the molding material can be prevented, and thus the size of the driving device can be made into small.