To provide a technology for regulating the movement (sliding) in the peripheral direction of an inner ring of a rolling bearing to a shaft part, in an installation structure of a camshaft integrally formed of a plurality of cam lobes and the shaft part, a crankshaft composed of the shaft part formed by bending and the rolling bearing composed of a divided structure.

This shaft structure 1 is composed of the rolling bearing 3 having the inner ring 4 composed of a plurality of first inner ring pieces 4A and second inner ring pieces 4B divided in the peripheral direction and the camshaft 2 having a journal part 2d for installing the rolling bearing 3. Locking parts 4a and 4a projecting in the axial direction are arranged in at least one of the inner ring pieces 4A and 4B, and locking object parts 2e and 2e mutually engaging with the locking parts 4a sand 4a are arranged in a partial area in the peripheral direction of the journal part 2d.