A metal mold for blow molding which may prevent a mold biting while maintaining a blowing performance and may mold a thermoplastic-elastomer article having a stable shape. In a blow molding metal mold provided with an annular loosely surrounding part for loosely surrounding an end part of a parison, a clearance between an outer peripheral surface of the end part and an inner peripheral surface of the loosely surrounding part at a parting line of the metal mold is larger than a clearance at the other parts than the parting line.