When a cylinder portion of an innerliner is positioned inside a mouthpiece and when an upper mold and a lower mold are brought together, a projection portion is provided on an outer circumferential member of the lower mold that closes a gap between a section of an upper mold side positioning outer circumferential surface following on from an inner circumferential end of an outer abutting surface and a portion of the innerliner where an inner circumferential surface abuts. As a result, the portion of the innerliner that is thermally deformed is prevented from being displaced radially inward of the mouthpiece along a first annular surface.