The calibration method for a multiple range finders system is proposed in this paper. Generally, multiple rangefinders are required to obtain the whole surface shape of a large object such as a human body. The proposed method solves range data registration by a prior calibration using a reference plane with rectangular markers. The world coordinates system is defined on the reference plane. Because range data have about two hundred thousands of 3-D points, the normal vector of the reference plane is accurately estimated by fitting the regression plane to the 3-D points. If the Z-axis of the world coordinates system for our calibration method is defined as the axis which cross meets the reference plane, it is determined by the normal vector. On the other hand the X and Y axes are defined as the horizontal line and vertical line of rectangular markers. They are determined by detecting and extracting the rectangular markers from the intensity image. Therefore, the orientation of each rangefinder is estimated based on the world coordinates system. In the experiments, the multiple rangefinders system which consists of twelve rangefinders is used. Experimental results indicate that the RMSE is 2.3 mm in the case of measuring a cylinder object.