Abstract: In a pair of wearing rings, the inner-cylinder wearing ring (5a, 5b) or the outer-cylinder wearing ring (4a, 4b) is formed of a carbon fiber reinforced plastic and constituted so that the coefficient of thermal expansion in the radial direction is −1×10−6/° C. to 30×10−6/° C. This makes it possible to maintain a clearance between the case wearing ring and the impeller wearing ring within a small fixed range even when the temperature rises due to rotation and when a high-temperature fluid is used. A pump provided with the wearing ring is excellent in stability and has a good efficiency.