PURPOSE: To bring an electric heater into contact with the outer circumferential surface of a nozzle proper by pressure by forming the outer circumferential surface of the nozzle proper and the inner circumferential surface of a cover member to the same tapered surface.

CONSTITUTION: An electric heater 12 is inserted and fitted to an outer circumference from the nose of a nozzle proper 4, and a cover member 9 is inserted onto the electric heater. Since the openings of the rear ends of the electric heater 12 and the cover member 9 are formed in size larger than the outer diameter of the nose section 4a of a nozzle, they can be inserted easily. Since the outer circumferential surface of the nozzle proper 4 and the inner circumferential surface of the cover member 9 are shaped to tapered surfaces at the same angle, the electric heater 12 can be pushed against the outer circumferential surface of the nozzle proper 4 by the cover member 9, and the pushing can be maintained by fixing a flange 10 to the end surface of an injection cylinder 1 by a bolt 16. Accordingly, each winding of the electric heater 12 is fast stuck to the outer circumferential surface of the nozzle proper 4, and the nozzle proper 4 is heated uniformly.