A crank bearing is disclosed that includes a semicircular upper bearing and a semicircular lower bearing, which can be split from each other. The upper bearing includes a first oil passage for introducing engine oil from the outside to a gap between the crank bearing and a crank journal, and a second oil passage for permitting the engine oil to flow in the circumferential direction of the crank bearing. The first oil passage includes an inner circumference opening, which is open to the inner circumference of the main bearing. The upper bearing includes a non-undercut portion in which no oil passage is formed on the trailing side of the inner circumference opening in the rotational direction of the crank journal. A chamfer oil passage for discharging the engine oil in the second oil passage to the outside from the axial direction of the crank bearing is provided in at least one of the lower bearing and a region on the proceeding side of the circumference opening in the rotational direction of the crank journal.