Main bearing for crankshaft for internal combustion engine

A main bearing for a crankshaft of an internal combustion engine comprises a pair of semi-cylindrical bearings (17, 18). An oil groove (17a) extends on an inner circumferential surface (17S) of one semi-cylindrical bearing (17) in a circumferential direction so that the center thereof in an axial direction aligns with that of an inlet opening (26) of a lubricating oil path (10a) in a journal section (10) of the crankshaft. The oil groove (17a) does not extend up to an axial direction groove (24A) formed at a joint portion of the semi-cylindrical bearings so that a separation inner circumferential surface (17S') extends between a circumferential direction end portion (17E) of the oil groove and the axial direction groove. The length (L1) of the separation inner circumferential surface is smaller than the length (L2) of the inlet opening in the circumferential direction.