To precisely and surely perform the quantitative supply of a raw material at a low cost.

When a screw feeder body 13 starts to drive, a raw material is put into the screw feeder body 13 from a measuring hopper 121, and fed to an extrusion molding machine side by the screw feeder body 13. On the other hand, a control device 14 receives the information related to the weight changed every moment of the measuring hopper 121 containing the raw material from a load cell 123 through an A/D converter as weight data, calculates the reducing quantity per unit time of the raw material to provide the present feeding quantity of the raw material, compares it with a preset target feeding quantity of the raw material, transmits a rotating speed control signal to a motor driving circuit on the basis of this comparison result, to regulate the rotating speed of a motor 133, so that the raw material is supplied to the extrusion molding machine in the target feeding quantity.