Disclosed is a bearing device including: a bearing housing made of an Al alloy and having a bearing holding hole; a sliding bearing having a cylindrical shape and forced into the bearing holding hole; and a shaft supported with an inner circumferential surface of the sliding bearing, wherein in the sliding bearing to be forced into, a plurality of hardened convex portions projecting toward the second circumferential direction end surface being formed on the first circumferential direction end surface, a plurality of hardened concave portions corresponding to the plurality of hardened convex portions being formed on the second circumferential direction end surface, a first hardened area being formed on each of the hardened convex portions of the first circumferential direction end surface and its vicinity, and a second hardened area being formed on each of the hardened concave portions of the second circumferential direction end surface and its vicinity.