To smooth the inner surface of an outer ring by finishing it by a forming tool forming no feeding trace and to further smooth without a burr and easily remove micro foreign matters attached thereto afterward by cleaning by barrel-finishing the inner surface.

This bearing device is formed by assembling a plurality of rolling bodies between the outer ring and an inner ring or a shaft, the inside diameter surface 1a of the outer ring 1, a track groove 1b, and a seal plate groove 1c are finished by the forming tool forming no feeding trace, and then treated by the barrel finishing. The forming tool 8 simultaneously grinds the whole of the inside diameter surface 1a of the outer ring 1, the track groove 1b, and the seal plate groove 1c.