A value of R/RBASE is not smaller than 0.75 and not greater than 0.87 where R represents a reference radius of curvature of a larger end face of a roller and RBASE represents a distance from an apex of a cone angle of the roller to a larger flange surface of an inner ring 13. A distance from an outermost surface of at least any one of an outer ring, the inner ring, and a plurality of rollers to a bottom of a nitrogen enriched layer is not shorter than 0.2 mm. A crowning profile is formed on a rolling surface of the roller.