To provide a manufacturing method capable of molding the thermoplastic elastomer molded product of high dimensional precision and excellent in productivity, and a manufacturing apparatus therefor.

The manufacturing method of the thermoplastic elastomer molded product comprises an injection molding process for injecting a thermoplastic elastomer in the fluid state in the cavity formed by a core 22 and a first outer mold 30 and subsequently cooling the same in the cavity to mold a parison, a heating process for separating the first outer mold 30 and heating the parison 11 up to a temperature capable of blowing up the parison 11 in the state attached to the core 22, and a blow molding process for putting the parison 11 in a second outer mold 50 in the state attached to the core 22, blowing compressed air in the parison 11 to expand the parison 11 not only to closely bring the parison 11 into contact with the inner wall surface of the second outer mold 50 but also to cool the same to mold the thermoplastic elastomer molded product 12.