To reduce cost and to prevent dew formation by forming an air flow passage using a duct wall part integrally stood and formed on the back side of a panel base material made of urethane foam.

The air flow passage 28 comprises the panel base material 22 made of hard urethane foam, rib-like duct wall parts 30 and 30 stood and formed on the back side of the panel base material 22, and a cover member 32 fixed so as to cover edges of the duct wall parts 30 and 30. The air flow passage 28 comprising the panel base material 22, the duct wall parts 30 and 30, and the cover member 32 connects an air conditioner unit 60 installed inside the panel base material 22 to an air outlet 62 disposed in the panel base material 22.