An oil-impregnated sintered sliding bearing formed of a porous iron-based sintered alloy with quenched structure and receiving a high surface pressure capable of reducing the number of finishing steps by cutting and grinding and providing a bearing performance equivalent to or higher than that of conventional bearings, wherein a plurality of ridge-and-groove lines having a height difference of 2 to 12.5 µm and extending in circumferential direction are axially arranged in parallel with each other by boring the bearing surface thereof to form a wavy surface in axial direction, and the portion thereof deeper by 10 to 60 µm from the outer layer of the bearing surface is formed dense to seal surface pores so as to reduce the pores opening to the outer surface to 1 to 10 percent by area, whereby the bearing can be used at a surface pressure of 6 kgf/mm 2 (58.5 MPa) or higher and a sliding speed of 2 to 5 cm/s.