PURPOSE: To measure the bend of a pipe without obstructing a manufacturing capacity by supporting the pipe like a beam supported at two pint, detecting distances between two or more points on the outer circumferential surface of the pipe in the longitudinal direction of the beam portion and a reference position while rotating the pipe in a circumferential direction and applying a processing to the pipe.

CONSTITUTION: A pipe P to be measured is freely supported by supporters S at two points in a longitudinal direction to be in the state of a beam supported at two point. A plurality of distance detectors D are arranged in a plane including the center lines CL of the supporters S and in positions apart from the reference surfaces of the supporters S by predetermined distances. The centers of the portions of the pipe P whereat it is supported by the supporters S are always positioned on the center lines CL of the supporters S. In the case of the pipe with a bend, when the pipe is rotated in a circumferential direction, the center of the pipe P passes the axial lines of the distance detectors D when the pipe approaches the detectors D closest and leaves the detectors D farthest. That is, the detectors D are arranged at two or more points in the longitudinal direction of the beam portion of the pipe P and the distance lbetween a reference position and the uppermost position of the outer circumferential surface of the pipe P is detected and, by using the distance l, the bend of the pipe P can be calculated on line with a good accuracy.