Two conflicting functions of sealing and lubrication of sliding faces are achieved for a long time. The sliding face of a rotating-side seal ring 3 is provided with dynamic pressure generation grooves 11 configured to communicate with the circumferential edge on the inner peripheral side of the sliding face and not to communicate with the circumferential edge on the outer peripheral side. A spring 7 is provided on the back side of a stationary-side seal ring 6 for pressing the stationary-side seal ring 6 against the sliding face of the rotating-side seal ring 3. A spring holder 8 is provided between the back side of the stationary-side seal ring 6 and the spring 7.