PURPOSE: To simplify a parison positioning method and to perform molding by merely moving a mold reciprocally, by extruding a parison in a vertical direction and sucking the outside surface of the parison to receive the parison in a cavity.

CONSTITUTION: In such a state that split molds 10, 12 are opened, a parison 22 is gradually suspended from a die 18 to be extruded by the length necessary for a molding. Subsequently, the outside surface of the parison 22 is sucked by the negative pressure of a suction part 28. Then, air cylinders 24, 26 are driven and the parison 22 suspended in a vertically downward direction is drawn in the direction of the air cylinders 24, 26. As a result, the parison 22 vertically suspended from the die 18 is curved along a cavity 14a and received in cavities 14a, 14b by clamping the split molds 10, 12. Thereafter, by blowing air in the hollow part of the parison from air injection ports 16a, 16b, a plastic pipe having a predetermined three-dimensional shape is molded.