1. A method for generating three-dimensional model data including an attached object attached to a machine tool and at least a part of the machine tool, comprising: a first step of storing three-dimensional model data into a storing section, the three-dimensional model data being related to a three-dimensional models of the at least part of the machine tool and the attached object attached to the machine tool, and including at least shape data that define shapes of the machine tool and the attached object; a second step, in which imaging means are used to image the attached object attached to the machine tool from two view points, i.e., a first view point and a second view point apart from the first view point, for generating two-dimensional image data at each of the view points; a third step of recognizing a shape feature of the attached object based on the two-dimensional image data generated in the second step; a fourth step of extracting, based on the three-dimensional model data of the attached object stored in the storing section, a shape feature of the attached object of the three-dimensional model data and checking whether the extracted shape feature matches the shape feature recognized in the third step, and thereby recognizing, out of the three-dimensional model data stored in the storing section, three-dimensional model data of the attached object imparted with the shape feature matching the shape feature recognized in the third step; and a fifth step of calculating a position and an attitude, of the three-dimensional model of the attached object, on the three-dimensional model of the machine tool, based on the shape feature recognized in the third step and the three-dimensional model data recognized in the fourth step, and thereafter, combining the three-dimensional model data of the attached object recognized in the fourth step with the three-dimension model data, stored in the storing section, related to the at least part of the machine tool and thereby generating the three-dimensional model data including the attached object and at least the part of the machine tool, based on the calculated position and attitude, the three-dimensional model data recognized in the fourth step, and the three-dimensional model data, stored in the storing section, related to the at least part of the machine tool, wherein each step is sequentially performed.