An injection foam molding machine of the invention includes: a movable mold platen; a fixed mold platen; a mold fastening hydraulic cylinder that is provided at each of four corners of both mold platens; a tie bar that is driven by the hydraulic cylinder to fasten the molds; two sets of mold opening and closing actuators that drive the movable mold platen to move close to or away from the fixed mold platen; two sets of dedicated core back devices; and a control device that controls the two sets of mold opening and closing actuators and the two sets of dedicated core back devices, wherein the control device includes a dedicated core back program that simultaneously controls the two sets of mold opening and closing actuators and the two sets of dedicated core back devices during a foaming core back operation of moving the movable mold platen away from the fixed mold platen.