A semi-cylindrical half bearing for a sliding bearing includes at least one axial groove formed on its inner circumferential surface that includes a smooth groove surface formed back away from the inner circumferential surface toward a radially outer side of the half bearing. The groove surface forms a convex curve toward the radially outer side in a cross-section perpendicular to the axial direction of the half bearing, and forms a straight line extending in the axial direction in a cross-section parallel to the axial direction. The half bearing further includes a plurality of axial narrow grooves formed on the groove surface so as to be back away from the groove surface toward the radially outer side, that extend in the axial direction of the half bearing.