PURPOSE: To fix a heat exchanger in an air-conditioning case with certainty as well as to improve the assembling property.

CONSTITUTION: A heat exchanger 11 is set up on an inner surface of an air- conditioning case 1 via a heat insulating material, and a rib 22 to be engaged with this heat exchanger 11 is installed in the inner surface of the case 1 projectingly. In addition, plural pieces of guide ribs 22 are set up on the inner surface of the case 1 at specified intervals, and these guide ribs 22 are set up in parallel with the moving direction of air in the air-conditioning case 1 along at least an upstream end face of the heat exchanger 11.