A sliding bearing 4 is constructed by an upper split bearing half 8 and a lower split bearing half 9. The upper split bearing half 8 has a sliding surface 8a, in which an oil groove 10 which allows an lubricating oil to flow therein is formed over the entire circumferential extent of the sliding surface 8a. The oil groove extends through a crush relief 8c to be open to a junction area 8b, and the oil groove has a bottom 10a which is formed so that a portion disposed toward the junction area as considered in the circumferential direction of the crush relief is located closer to the center of the upper split bearing half in comparison to a central portion. An ingress in large quantities of foreign particles within the oil groove onto the sliding surface of the sliding bearing and into a connecting rod bearing after passing through a lubricating oil feed passage is suppressed, and an oil leakage through the crush relief is reduced, allowing a lubricating oil pressure to be secured and augmented.