PURPOSE: To prevent rain drop from entering by projecting a flange from a periphyreral edge of a ventilating port, bending outward an upper end of the flange, and covering the flange with an upper cover having an air hole at its lower end.

CONSTITUTION: A ventilating port 3 is formed on a roof 1 oppositely to an installation position of a ventilator 2. A flange 4 is projected from a peripheral edge of the ventilating port 3. The flange 4 is cylinrically formed, while air is exhausted outside a cubicle through the flange 4. An upper end of the flange 4 is bent outward to form a flashing portion 5. The flange 4 is covered with an upper cover 7 having an air hole 9 on its lower end. It is thus possible to prevent rain drop from entering and to sufficiently perform ventilation, while to reduce number of items, save manufacturing steps.