To lengthen service life of a tapered hole bearing and to facilitate assembly work of the tapered hole bearing.

Mounting structure is to provide a flange part 1d on the large diametrical side of a tapered surface 1c of a sleeve member 1, to provide a nut member 2 on the small diametrical side of the tapered surface and to regulate a position in the axial direction (push-in quantity) by constraining a tapered hole bearing from both sides. Consequently, it is possible to extend service life of the bearing by holding an inside clearance of the tapered hole bearing in a proper state and to facilitate assembly work simultaneously. Additionally, it is possible to adjust the position in the axial direction of the tapered hole bearing by interposing a spacer 4 between the flange part 1d and the tapered hole bearing or constituting the flange part of the nut member.