This cylinder block comprises: a cylinder block body in which a plurality of cylinder chambers are formed around a rotary shaft; a plurality of first parts to be detected which are formed, on the outer circumferential surface of the cylinder block body, at predetermined first intervals in the circumferential direction; and one or more second parts to be detected which are formed, on the outer circumferential surface of the cylinder block body, at second intervals different from the first intervals with respect to an adjacent first part to be detected.