Provided are a control device and a control method for an injection molding machine that carries out a punching step with high reliability. A control device for an injection molding machine, the control device being equipped with: a mold opening/closing unit that integrally moves a fixed mold and a moving mold of a mold of the injection molding machine in the opening direction from a state where the mold is closed, thereby creating a gap between the fixed mold and a mounting plate; an insertion member control unit for inserting an insertion member into the gap; an assessment unit for assessing whether the insertion member has been inserted into the gap; and a push control unit for pushing out a punching pin when the insertion member has been assessed to have been inserted into the gap.