PURPOSE: To enhance the molding accuracy and at the same time shorten the molding time of the titled device by a method wherein estimated values are compared with the standard temperature distribution and pressure distribution and the feeding rate of molding material, the driving speeds of a screw and of a piston and the heat quantity generated at a heater are controlled so as to make the estimated values coincide with the standard distributions.

CONSTITUTION: A controlling device 25 calculates the total heat quantity held by the resin in a cylinder 1 and compares it with the total heat quantity to be held by resin under the predetermined ideal temperature distribution. When the deviation is shown between both the total heat quantities, the controlling is done by regulating power supplies to respective inductors 14-1W14-5 so as to bring said deviation to zero. Similarly, as for pressure, the degree of fusion and viscosity of resin are ideally controlled by means of the controlling device 25 based upon the values detected by pressure detectors 16-1W16-14 by controlling the driving speed of a screw 2 and the shifting speed of a piston 34. Thus the temperature and pressure of the resin extruded from the cylinder is kept at the optimum state for treatment at all times and accordingly the generation of pores, crazes, strains and the like of a product can be reduced and at the same time its molding accuracy can be enhanced and its molding time can be shortened.