Abstract: A single-piece outer race ring 3, a sleeve-like spacer 11, a plurality of first balls 4, a conventional ball bearing unit 7, a stepped-diameter shaft 1 and the like are assembled into a compound bearing assembly by a bearing maker with high accuracy to enable a user to be free from a cumbersome assembling work of rotating portions or cylindrical rotary shaft and its bearing means of a computer and its peripheral devices. In use, the compound bearing assembly is coaxially mounted in the cylindrical rotary shaft and the like at the user's end to rotatably support the cylindrical rotary shaft and the like in the computer and its peripheral devices.