To provide a measuring device by which the centering/facing of a piping machining machine disposed on the piping can be carried out simply and easily.

The device is provided with a piping machining means by which cutting and machining the piping 1 temporarily fixed and disposed inside the piping 1 can be made possible and a measuring means for measuring the mounting condition of the piping machining means against the piping 1 mounted on a rotor 16 in said piping machining means. The above measuring means is mounted on the above rotor 16 via a ring mechanism 32 and a touchingly movable contact shoe 33 is provided by following a machining standard line 44 marked on the outer peripheral face of the piping 1. The above ring mechanism 32 is made to be a movable in the three axial direction of a coordinate in which the rotation center of the above rotor 16 is made to be an original point and by making the displacement in the three axial direction accompanied by the rotation of the above contact shoe 33 detectable, the fixing position for the above piping machining means is made correctable based on this detected value.