PURPOSE: To obtain an S-shaped hollow tube and a U-shaped bent tube large in the curve by blow molding by rotating a nozzle body on the center shaft while provided with a means of vertically moving it in a central hole of a nozzle holder.

CONSTITUTION: A nozzle comprise a nozzle holder 5 and a nozzle body 6 fitted into the inner surface thereof and the nozzle holder is mounted on an extruder cylinder. The nozzle body 6 is rotated on the center shaft in a hole provided in the center of the nozzle 5. It has functions of fixing a motor 15 and fixing a cylinder for vertically sliding the nozzle body in the central hole of the nozzle holder. A parison P extruded from the nozzle body is injected accurately along a molding groove 36 with a bend according to level, inclination and step and blow molded at an air suction port not illustrated after upper and lower dies are closed.