The present invention provides a half thrust bearing in a semicircular ring shape for receiving an axial force of the crankshaft of the internal combustion engine, including thrust reliefs formed adjacent to both circumferential end portions of a slide surface which receives the axial force, so that a wall thickness of the half thrust bearing becomes thinner toward the circumferential end portions, wherein at least the thrust relief on a rear side in a rotational direction of the crankshaft has a thrust relief length which becomes larger toward an outer end portion from an inner end portion in a radial direction of the half thrust bearing. The present invention also provides a bearing device including the above half thrust bearing, a crankshaft, a pair of half bearings supporting a journal portion of the crankshaft, and a bearing housing having a holding hole for holding the pair of half bearings.