A neck crystallization method includes inserting a core into the neck, heating the neck using a heater group disposed along a transfer direction while rotating the preform on its axis, and transferring the preform along the transfer direction in a state in which the core is inserted into the neck, and cooling the neck of the preform in a state in which the core is inserted into the neck. The heating of the neck includes a first step that drives first heaters positioned on the upstream side in the transfer direction at a first power, and a second step that drives second heaters positioned on the downstream side of the first heaters at a second power that is lower than the first power until the temperature of the neck reaches a crystallization temperature zone.