A mechanical seal has a seal cover attached to an outer surface of a device body, a fitting surface through which a shaft is insertable, and defines a space further away from a machine than the fitting surface. A quenching path penetrates the space and supplies quenching fluid therein. A first seal ring has a movement surface fitted to the fitting surface and a seal surface inward of the space section. A second seal ring has a relative slide seal surface in tight contact with the seal surface of the first seal ring and a seal surface that faces a restriction surface. A seal collar holds the second seal ring in a sealed state and is sealingly fixed to the shaft. A packing is in tight contact with the seal surface of the second seal ring and the restriction surface to prevent quenching fluid from leaking out of the machine.