A half bearing (31, 32; 41, 42) constituting a sliding bearing that supports a crankshaft of an internal combustion engine, the half bearing (31, 32; 41, 42) having a semi-cylindrical shape and including an inner circumferential surface and an outer circumferential surface, the half bearing (31, 32; 41, 42) comprising: at least one protrusion, the protrusion projecting outward in a radial direction from the outer circumferential surface, wherein a recessed portion recessed inward in the radial direction from the outer circumferential surface is formed over an entire circumferential length between the protrusion and a circumferential end surface of the half bearing (31, 32; 41, 42), the protrusion is located between both end surfaces of the half bearing (31, 32; 41, 42) in an axial direction, the recessed portion includes a recessed portion bottom surface that is parallel with the axial direction of the half bearing (31, 32; 41, 42) when seen in a section that is parallel with the circumferential end surface, two recessed portion side surfaces that perpendicularly intersect the axial direction of the half bearing (31, 32; 41, 42) at both ends of the recessed portion in the axial direction of the half bearing (31, 32; 41, 42), and two recessed portion curved surfaces that connect the recessed portion side surfaces to the recessed portion bottom surface, two radial-direction grooves are formed in the circumferential end surface of the half bearing (31, 32; 41, 42) relative to the protrusion, each of the two radial-direction grooves being adjacent to each of the recessed portion side surfaces, an extension length of the radial-direction grooves is greater than a depth of the recessed portion when seen from the direction orthogonal to the circumferential end surface 76, the radial-direction grooves extend in the radial direction along the recessed portion side surfaces from the outer circumferential surface toward the inner circumferential surface of the half bearing (31, 32; 41, 42), the radial-direction grooves being separated from the recessed portion at a midpoint of the extension, an inner circumferential surface-side end portion in an extending direction of the radial-direction grooves is located between the recessed portion bottom surface and the inner circumferential surface of the half bearing (31, 32; 41, 42), and a groove width and a groove depth of the radial-direction grooves decrease from the position separated from the recessed portion toward the inner circumferential surface-side end portion and reach zero at the inner circumferential surface-side end portion. at least one protrusion, the protrusion projecting outward in a radial direction from the outer circumferential surface, wherein a recessed portion recessed inward in the radial direction from the outer circumferential surface is formed over an entire circumferential length between the protrusion and a circumferential end surface of the half bearing (31, 32; 41, 42), the protrusion is located between both end surfaces of the half bearing (31, 32; 41, 42) in an axial direction, the recessed portion includes a recessed portion bottom surface that is parallel with the axial direction of the half bearing (31, 32; 41, 42) when seen in a section that is parallel with the circumferential end surface, two recessed portion side surfaces that perpendicularly intersect the axial direction of the half bearing (31, 32; 41, 42) at both ends of the recessed portion in the axial direction of the half bearing (31, 32; 41, 42), and two recessed portion curved surfaces that connect the recessed portion side surfaces to the recessed portion bottom surface, two radial-direction grooves are formed in the circumferential end surface of the half bearing (31, 32; 41, 42) relative to the protrusion, each of the two radial-direction grooves being adjacent to each of the recessed portion side surfaces, an extension length of the radial-direction grooves is greater than a depth of the recessed portion when seen from the direction orthogonal to the circumferential end surface 76, the radial-direction grooves extend in the radial direction along the recessed portion side surfaces from the outer circumferential surface toward the inner circumferential surface of the half bearing (31, 32; 41, 42), the radial-direction grooves being separated from the recessed portion at a midpoint of the extension, an inner circumferential surface-side end portion in an extending direction of the radial-direction grooves is located between the recessed portion bottom surface and the inner circumferential surface of the half bearing (31, 32; 41, 42), and a groove width and a groove depth of the radial-direction grooves decrease from the position separated from the recessed portion toward the inner circumferential surface-side end portion and reach zero at the inner circumferential surface-side end portion.