To provide a double wall structure in which electric power consumption used for cooling and heating is saved.

Outside of an RC wall, a silver sheet is pasted in double on an insulating member 4, and additionally, an air layer 5 is provided. The double silver sheets are pasted also on the air layer member to fix an exterior member 7 to the outside of the silver sheets with a fixing means, driving the exterior member into the RC wall to be finished with exterior tiles or the like. A gallery box 1 is connectively installed on the wall at the upper and lower of the air layer, guiding the air from below to flow upward by opening/closing the blades 2 of the gallery box with the oscillation of the motor, exhausting the air from the air layer. Thereby, the temperature on the wall surface is lowered in summer, while the temperature in the air layer is increased by closing the gallery box in winter to shut off the temperature of the outer wall.