There are provided tapered roller bearings which support a pinion shaft. Inner races have large rib faces each having a recessed surface shape on which large-diameter end faces of tapered rollers slide. The surface roughness of the large-diameter end face is .sigma.1 [.mu.mRa] is 0.025 or more. In addition, assuming the surface roughness of the large rib face is .sigma.2 [.mu.mRa], (.sigma.1.sup.2+.sigma.2.sup.2).sup.1/2 is 0.17 [.mu.mRa] or less. The sliding portion of the large-diameter end face and the sliding portion of the large rib face are made of a carburized steel, and the carbon content in a matrix phase in a surface layer portion of each of the sliding portions to a depth of 50 .mu.m from a surface is 0.8 wt % or more, the surface hardness thereof is in the range of Rockwell C63 to 67, and a surface retained austenite amount is set to be 20% or more and 25% or less.