Abstract: The invention relates to injection molding and is provided with a heating cylinder, an injection nozzle disposed at the forward end of the heating cylinder, a resin feed means, such as screw, which feeds molten resin to a portion in the vicinity of the forward end of the heating cylinder. Also provided is a piston means, such as a plunger, which has a stop valve mechanism that closes when it is moved in an injection direction and is opened when it is moved in a counterinjection direction and injects molten resin, fed to a portion in the vicinity of the forward end of the heating cylinder, into a cavity through the injection nozzle, whereby, through driving of the resin feed means and the piston means, charging of molten resin into the forward end of the heating cylinder and injection of the molten resin into a cavity are carried out partially concurrently.