To make the axial dimension of a bearing compact and facilitate the machining of inflow and outflow ports of lubricating oil by arranging side rings having a small clearance with an outer ring inside surface and having a lubricating oil outflow port on both end parts of a cylindrical inner ring.

This bearing is formed of an outer ring 2 having an inner ring collar 3 in the center, a cylindrical inner ring 1, and a plurality of cylindrical rollers 4 held by a retainer 9. Further, side rings 5, 6 having a small clearance 10 with the inside surface of the outer ring 2 and guiding the cylindrical rollers 4 are provided on both ends of the inner ring. Radial lubricating oil inflow ports 7, 7 are formed in the parts between the cylindrical rollers 4 of the inner ring 1 as alternately directed oblique holds, and axial lubricating oil outflow ports 8, 8 are formed on both the side rings 5, 6. Since no oil seal is used in this structure, the axial width of the bearing can be made compact, and the machining of the inflow and outflow pots of lubricating oil can be facilitated.