Measurement device for annular assembly and method thereof, and method of manufacturing rotating machine

A measurement device (1) for a ring-shaped assembly (60). Said measurement device (1), which measures relative radial positions on a ring-shaped assembly (60) in which a plurality of assembled members (62) that are lined up in a circumferential direction are assembled onto a ring-shaped member (61), is provided with the following: a first contact section (19) that can slide in the circumferential direction of the ring-shaped member (61) and contacts a reference surface (4) that is continuous in said circumferential direction; a second contact section (25) that can press against an opposing surface (5) that faces the opposite radial direction from the aforementioned reference surface (4) of the ring-shaped member (61); a base section (6) that supports the first contact section (19) and the second contact section (25); a third contact section (29) that contacts measurement-target sections (62a) of the abovementioned assembled members (62); a connecting section (7) that connects the third contact section (29) to