A bearing device, including a crankshaft, a pair of half bearings each having crush reliefs formed adjacent to both circumferential ends thereof, a bearing housing in which a retaining hole is formed for retaining the pair of half bearings, and one half thrust bearing having a semi-annular shape arranged adjacent to the retaining hole. The half thrust bearing includes thrust reliefs formed adjacent to both circumferential end portions of a sliding surface receiving an axial force of the crankshaft so that its wall thickness is made thinner toward the circumferential end surface, and a thrust relief length at an inner end portion of the thrust relief positioned on a rear side in the crankshaft rotational direction is formed to be larger than a thrust relief length at an inner end portion of the thrust relief positioned on a front side in the crankshaft rotational direction.