PURPOSE: To perform a uniform cooling on the entire surface of a substrate by a method wherein a heat conducting material, having a concaved surface on the side opposite to the substrate, is coupled and an inflow and an outflow nozzles are provided along the extending direction of the concaved surface.

CONSTITUTION: A heat conducting material 32, with a concaved surface on the side opposite to a wiring substrate 21, is coupled to a circuit substrate 22 of the circuit device 24. Then, the flowin nozzle 42 and the flowout nozzle 44, which were formed in parallel with the extending direction of the concaved surface 31, are provided back to back. As a result, cooling gas 5 runs smoothly along one half of the heat conducting material 32 in the extending direction of the concaved surface 31, smoothly runs along the other half of the concaved surface 31, and then runs into the flowout nozzle 44 from the side of an opening 43. Accordingly, there generates no temperature difference between the center part and the outer circumferential part of the heat conducting material 32.