PURPOSE: In a car air-conditioner unit connecting structure, to facilitate insertion of an intermediate unit while to achieve reliable sealing by constructing the connection opening of intermediate and fixed units with a tapered inner insertion frame, receiving frame and resilient sealing member.

CONSTITUTION: The insertion starting end 43 of a tapered inner insertion frame 42 of an intermediate unit 3 is inserted into the receiving port 52 of a receiving frame 52 of a fixed unit 2 and pushed in. Since the inner insertion frame 42 and a resilient seal member 6 will never pressure contact from the start of insertion untill immediately before completion, it can be inserted smoothly while since the inner insertion frame 42 is tapered the lateral sides of said frame 42 will contact with said member 6 immediately before completing insertion, and upon completion of insertion the front end of said frame 42 will also pressure contact with said member 6 to provide complete sealing. Consequently the intermediate unit can be connected smoothly resulting in reliable sealing.