Reduction of size and weight are required in a development of machine tools that are mainly used in prototyping purposes. It is generally known, however, that when the reduction of size and weight of the structure were both pursued the machining accuracy can possibly be degraded due to insufficient stiffness. It is important to increase the specific stiffness and thermal stability of a machine tools structure for better machining accuracy. In this study we have applied a sheet of carbon fiber reinforced plastic and a sheet of aluminum honeycomb. A sandwich structure made of both materials and the ribs made of carbon fiber reinforced plastic was proposed. The proposed structure showed the increased specific stiffness and the thermal stability which are suited to the machine tools of high accuracy. We investigated the basic performance of the proposed structure by using several beam-shaped samples, in which the static stiffness and thermal expansion was measured and compared. The inserted ribs in the proposed structure was revealed to be suppressing the thermal expansion of the aluminum honeycomb core. After the basic investigation, a 5-axis machining center with the proposed structure was designed. The mechanical and thermal performance of the structure was tested in the finite element analyses. Finally the machining center was manufactured.