Shaping method of the sealing ring, shaping device and the seal ring of the seal ring

A seal ring whose abutment joint portion is opened is fitted into an annular gap while the abutment joint portion is substantially closed. The annular gap is formed between an inner circumferential surface of a hole portion provided in an outer circumferential jig and an outer circumferential surface of an inner circumferential jig disposed in the hole portion, and has a heating region and a cooling region. The seal ring is passed through the heating region and then passed through the cooling region in the annular gap. The outer circumferential jig and the inner circumferential jig are maintained at a constant temperature higher than a glass transition temperature of a resin material for the seal ring in the heating region, and maintained at a constant temperature lower than the glass transition temperature of the resin material for the seal ring in the cooling region.