Rotation restricting device for rotation machine

A rotation restricting device for rotation machine, comprising a rotation shaft supporting body, a rotation shaft provided so as to be rotatable with respect to said rotation shaft supporting body, a fixing ring fixed on an end portion of said rotation shaft, a position finding dog protruding in a radial direction and provided on said fixing ring, a rotary cam disposed concentrically outside said rotation shaft, a cutaway portion formed on said rotary cam, a rotary dog protruding toward said rotation shaft supporting body and disposed on said rotary cam, and a stopper protruding toward said rotary cam and provided on said rotation shaft supporting body, wherein said position finding dog is accommodated in said cutaway portion and said fixing ring can be relatively rotated within a range in space as formed by said cutaway portion with respect to said rotary cam, said stopper is positioned on a locus of rotation of said rotary dog, and said rotary cam rotates relative to said rotation shaft supporting body until said rotary dog comes in contact with said stopper, wherein a rotation angle of said rotation shaft is a sum of a relative rotation angle of said fixing ring with respect to said rotary cam and a relative rotation angle of said rotary cam with respect to said rotation shaft supporting body.