A green tire of a pneumatic tire, including a cylindrical annular structure, an unvulcanized rubber layer, which will become a tread portion, provided along a circumferential direction of the annular structure on an outer side of the annular structure, and a carcass portion including fibers covered with rubber, provided on at least both sides in the width direction of a cylindrical structure including the annular structure and the unvulcanized rubber layer, is disposed in a vulcanization mold. The vulcanization mold is split into the side plates and the sector at a position on the inner side in the width direction of the annular structure. Next, the bladder inside the green tire is pressurized after closing the side plates and prior to closing the sector. Then the sector is closed and vulcanization is started.