An injection molding machine includes a plasticating unit for plasticating a thermoplastic resin, and an injecting unit connected to the plasticating unit through a connecting passage to inject the plasticated resin into a mold. The injecting unit A includes a rotary pump having a suction port connected to the plasticating unit through the connecting passage and a discharge port connected to the mold. The plasticated resin is intermittently injected into the cavity of the mold through the injection port by means of the rotary pump. In the connecting passage, an accumulator is provided which reserves the resin plasticated in the plasticating unit in an amount equal to or more than the shot capacity, and feeds the resin to the rotary pump.