A power transmission apparatus is disclosed. A pulley is journalled through a ball bearing on the outer periphery of a bearing support portion arranged on a housing, and a metal ring is fitted on the inner periphery of the pulley. The outer ring of the ball bearing is press-fitted into the inner periphery of the metal ring, and a punch is forcibly pushed into a front-side end surface of the ring. In this way, punched holes each having a sectional area progressively increased from the rear to front side are formed, and the portions of the metal ring near to the inner periphery than the punched holes are pushed out and caulked. Thus, caulked portions are formed to fixedly caulk the outer ring.