To provide a fixing structure of an adjust nut having simple structure, and to provide a manufacturing method of the adjust nut.

The fixing structure of an adjust nut includes an adjust nut 20 and a bearing cap 30. The adjust nut 20 comprises an outer circumferential face 20c on which a screw 21 is provided and an end face 20a disposed an axial end of the outer circumferential face 20c. The bearing cap 30 is screwed on the adjust nut 20. The adjust nut 20 has a projection 26. The projection 26 projected into an axial direction from the end face 20a to the outer circumferential face 20c is engaged with the bearing cap 30 by plastic deformation to the outer circumferential face 20c.