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 model data into a storing section, the model data are related to a three-dimensional model of the at least part of the machine tool and the attached object attached to the machine tool, and include 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 for recognizing a shape feature of the attached object based on the two two-dimensional image data generated in the second step; a fourth step for recognizing model data of the attached object imparted with the shape feature, based on the shape feature recognized in the third step and the model data of the attached object stored in the storing section; and a fifth step for, based on the shape feature and the model data each recognized in the third step and the fourth step, calculating a position and an attitude, of the three-dimensional model of the attached object, on the three-dimensional model of the machine tool, and thereafter, generating the three-dimensional model data including the attached object and at least the part of the machine tool, based on calculated position and attitude, the model data recognized in the fourth step, and the model data, stored in the storing section, related to the at least part of the machine tool, wherein each step is sequentially performed.