PURPOSE: To reuse the cut portions of a molding materials by a method in which the hollow cylinder of three-layered structure is molded, and the projected portions to be cut off are molded to be single layer structure.

CONSTITUTION: A preform 1 consisting of an outer layer 1a, an intermediate layer 2, and an inner layer 1b is heated and inserted into a blow mold B for forming a hollow molding by removing a neck portion 3 held by a neck mold 4. An extension rod 5 is inserted from the upper part of the neck mold 4 into the preform 1 and extended toward the axial direction, air is blown into the preform 1 to expand it radially to form a hollow molding 6 having a projected portion 7 integrally formed on the upper part of the torso 6a and the bottom 6b. In this case, the outer layer 1a, the intermediate layer 2, and the inner layer 1b become the three layer consisting of inner, outer and intermediate layers, and the neck portion 3 becomes the monolayer of the projected layer 7. The projected portion 7 is cut off at the portion 7a and reused as molding material. The remaining hollow molding 6 is seamed with a metal cover 10 to become a container.