In an embodiment, a pair of sliding components that slide relative to each other is included. One of the sliding components is a stationary-side seal ring 2, and the other sliding component is a rotating-side seal ring 3. The seal rings 2 and 3 have sliding faces S2 and S3 extending radially, respectively, for sealing sealed fluid against leakage. The sliding faces S2 and S3 are provided with a static pressure groove 22 communicating with a sealing gas supply passage, and pumping grooves 5 capable of controlling the radial flow of sealing gas to a flow from the low-pressure fluid side to the high-pressure fluid side by relative sliding of the sliding faces. By controlling the radial flow of sealing gas at the sliding face, the amount of flow of the sealing gas flowing to the low-pressure fluid side is reduced to improve sealing performance.