a method for controlling an injection molding machine involving the steps of : detecting , by a screw position detector , a position of a screw of the injection molding machine immediately before the start of injection , to produce a detecting signal ; comparing the detecting value with a predetermined value for a plasticizing / measurement position set in a metering position setter , to calculate any deviation therebetween ; and adding / substracting the deviation to or from predetermined values representative of switching - over positions set in switching - over position setters , thereby keeping constant an actual screw stroke from the plasticizing / measurement position to the switching - over position for every shot of the injection molding machine .