An artificial joint with smooth metal surface is usually used. However, it is not clear that the smooth surface is optimal for the improvement of the wear resistance of an artificial joint. Then, in this work, the relationship between the sliding surface geometry of a metal component and the wear of an UHMWPE component was investigated by the 2 axes pin-on-plate test. By the test, it was shown that the dimpled metal surface is optimal for the improvement of the wear resistance of an artificial joint.