To lighten the weight and to enhance the quietness and safety by using thermal conductive elements exhibiting heat exchange action by Peltier effect.

An exhaust heat chamber 5b has three small-size air intake fans 12a arranged in the right side and three air exhaust fans 12b arranged in the left side. A cooling chamber 5c forming a space by a cooling unit 9 and a partition board exposes the surface of heat radiating parts 9c of the cooling unit 9. The cooling unit 9 and the partition board are connected by four supports 10 so as to secure the rigidity of the cooling chamber 5c. Four air blower fans 13 are equipped between the top plate and the partition board and vent holes 13a are opened in the top plate and the partition board. The cooling unit 9 is so formed that a plurality of thermal conductive elements 9a are aligned into a grid and pinched into a sandwich state between heat absorbing parts 9b and the heat radiating parts 9c. The thermal conductive elements 9a thus exhibit the heat exchange action between the heat radiating parts 9c and the heat absorbing parts 9b by Peltier effect.