Method for hot crystallization of neck portion in preform of biaxial stretch blow molded bottle and jig for use in the method

A method for thermally crystallizing a neck of a primary molded product for forming a bottle-shaped container made of polyethylene terephthalate as principal ingredient, said neck having a functional part and a neck ring at a lower end thereof, said functional part being formed with screw threads at an upper portion thereof and a bead ring below the screw threads, said method comprising: heating the neck, and then squeezing the bead ring heated to the heat-deformable temperature, from outside so as to form an outer diameter of the bead ring within a dimensional tolerance for deformation with regard to sealing effect. Preferably, the primary molded product includes at least one resin layer(s) made of polyethylene terephthalate as principal ingredient and at least one gas barrier material layer(s), and has a multilayer structure. Also, preferably, the bead ring is squeezed by 0.1 mm to 0.4 mm in terms of an outer diameter of the bead ring immediately after a completion of heating. Also, a jig for the above method is provided.