PURPOSE: To enhance productivity so as to perform preheating directly prior to vulcanization within a vulcanization stand-by time, by inserting a green tire into a pair of vulcanization molds to form a hermetically closed space while allowing a pressure medium to act on said space under heating.

CONSTITUTION: When a green tire A is held at the predetermined position between closure discs 1, 2 held under a largely opened state and the closure discs 1, 2 are closed and matched, bead contacting seats 3 are contacted with the tire bead parts to mold the tire into an almost final shape. Thereafter, air is introduced into the formed hermetically closed space including the interior of the tire body under pressure to raise the pressure of the space to pressure slightly higher than the atmospheric pressure while a current is supplied to a heater 4 and a fan 5 to heat the green tire A from the interior thereof. After preheating, the closure discs 1, 2 are opened to take out the heated green tire A. The tire A has a shape near to the final shape and succeedingly inserted into a vulcanization mold to perform vulcanization.