Seal body and gas sealing mechanism

A seal body (20) includes a gasket main body (21), a spring (22) and a rigid ring (30). The seal main body (21) is resistant to the gas to be sealed, forming a recessed groove (21c) by arrangement of opposing lips (21a, 21b). The spring (22) is a molded product obtained by deforming a spring steel plate in a circular object with a V-shaped cross-section. The spring (22) is inserted in the recessed groove (21c) of the seal main body (21) and spread by application of their elastic force the lips apart. The rigid ring (30) has a circular shape, is arranged inside the spring (22) and supports an inner surface of the spring (22) when the spring is compressed, so that the open end of the spring (22) narrows. Thereby, the rigid ring (30) restricts the deformation of the spring (22) on an elastic deformation range.