PURPOSE: To make the size and weight of a machine tool small and enhance its performance or the like for machining accuracy, by making the height of a slide way distant from the tool of the machine tool, larger than that of another slide way near the tool, so that the slide way of the larger height receives an external force.

CONSTITUTION: In a machine tool such as a machining center, an external force F acts to a tool G in machining work and has a component perpendicular to the longitudinal direction of each of slide ways A, B and parallel with the mounting face D of a pedestal C. It is supposed that the external force F consists of only the component perpendicular to the longitudinal direction of each of the slide ways A, B and parallel with the mounting face D. Since the external force F acts to the slide way B of larger height than the other slide way A, a movable rest E receives moment M around the point of the slide way B which receives the external force F. The larger than height of the slide way B is, the smaller than magnitude of the moment M is. Thus, the height of the slide way B is increased to enhance the machining accuracy of the machine tool while reducing its size and weight.