A sliding surface of a second sliding component is provided with a plurality of second positive pressure generation grooves communicating with a leakage side space, extending in a relative rotation direction of the second sliding component, and having closed terminating end portions, a sliding surface of a first sliding component is provided with a plurality of first positive pressure generation grooves communicating with the leakage side space, extending in a relative rotation direction of the second sliding component, and having closed terminating end portions, and the sliding surface and the sliding surface slide on each other at least in such a manner that the first positive pressure generation grooves and the second positive pressure generation grooves overlap and intersect with each other.