An injection apparatus includes an actuating cylinder, an accommodating chamber, and a volume changing part capable of changing the volume of the accommodating chamber. The actuating cylinder has an operation chamber and a piston accommodated in the operation chamber, and supplies an incompressible fluid to the injection cylinder by forcing out the incompressible fluid inside the operation chamber with the piston. The accommodating chamber is connected to the operation chamber, and holds at least some of the incompressible fluid that flows out from the operation chamber due to the piston being pushed out. The volume changing part expands the volume of the accommodating chamber, at the latest simultaneously with the start of acceleration of the actuating cylinder, and stops the expansion of the volume when the operating speed of the piston of the actuating cylinder has reached a desired speed.