PURPOSE: To prevent the outer surface of a preform from being excessively heated by intermittently radiating to heat the preform.

CONSTITUTION: Preforms P1, P2 are fed to a rear stage heating station 6 via a front stage heating station 5. A plurality of near infrared heaters are arranged in upper and lower row states at one side of a conveying route of its front stage conveying route 61, and a shutter plate is provided to the preforms P. The plate is raised to radiate to heat while the preforms P are conveyed by a transfer tool 82. On the other hand, a cooling mechanism for cooling the preforms P by a supply fan is provided at a rear stage side conveying route 62 of the station 6. Its cooling operation is started when the temperature of the heated preforms P exceeds a peak value. As a result, since an inner and outer surface temperature difference can be reduced, the excess heating of the outer surface to be deteriorated can be avoided.