Half thrust bearing

A half thrust bearing having a semi-annular shape for receiving axial force of a crankshaft of an internal combustion engine, wherein

• the half thrust bearing comprises a slide surface which receives the axial force, and a back surface on an opposite side to the slide surface, a bearing wall thickness between the slide surface and the back surface being constant,
• the half thrust bearing comprises a flat center region including a circumferential center of the half thrust bearing, and two end regions on both circumferential sides of the center region, each end region extending from each circumferential end of the half thrust bearing toward the circumferential center over a circumferential angle of 5° or more and 35° or less, and
• a reference surface is defined by an imaginary plane which is perpendicular to an axial direction of the half thrust bearing, parallel to the slide surface in the center region of the half thrust bearing and located on a slide surface side of the half thrust bearing away from the slide surface, wherein an axial distance between the slide surface and the reference surface is minimum in the center region, and continuously increases in a circumferential direction from a center region side toward a circumferential end side at any radial position in each end region.