By providing projections 4 extending intermittently or continuously on the inner wall face of the cylindrical shaped bladder 2 at an inclination to the circumferential direction thereof, during vulcanization of a green tire G when the inside of the bladder 2 is filled by injecting with hot water as heating medium H and pressurizing medium, or steam as heating medium H and a gas as pressurizing medium, the heating medium H is guided along the projections 4 and flows in the circumferential direction of the expanded bladder 2, and flows in a rotating motion in the vertical direction of the bladder 2, and as a result of the synergistic action of the circular flow of the heating medium H in the circumferential direction of the bladder and the rotating flow in the vertical direction of the bladder, the temperature difference of the bladder 2 is sufficiently reduced.