To reduce friction resistance to be applied to a resin in an injection process.

An injection apparatus is equipped with a heating cylinder 11 having a resin supply port 15 formed thereto at a predetermined position, a flight part 21 wherein flights 23 are formed to the outer peripheral surface of a screw main body and the screw head 27 arranged to the front end of the flight part 21 and has the screw 12 arranged in the heating cylinder 11 so as to freely rotate, advance and retreat and the hopper 16 attached to the resin supply port 15. An opening-closing member is arranged to the lower end of the hopper 16 to take a communication position allowing the heating cylinder 11 and the hopper 16 to communicate with each other and a cut-off position cutting off the heating cylinder 11 and the hopper 16. When the opening-closing member is placed at the open-close position, the load of the resin in the hopper 16 is received by the on-off member and not applied to the resin in the vicinity of the resin supply port 15.