PURPOSE: To eliminate the need to remove a ceiling plate when a ventilation fan is to be removed and to facilitate the positioning of fixing of the ventilation fan by a method wherein the main body of the ventilation fan is fixed to the ceiling plate in the room.

CONSTITUTION: The main body 1 of a ventilation fan is provided with a discharging port 4, suction ports 5 and 6. The main body 1 of the ventilation fan is connected to an auxiliary frame 7 by screws 13 and 19. The auxiliary frame 7 is made such that a discharging fixing plate 9 having a coupling pipe 8 and a sucking fixing plate 11 having a coupling pipe 10 are fixed by screws 12. The auxiliary frame 7 is fixed to the ceiling plate 17 by a wooden frame 16. In order to remove the main body 1 of the ventilation fan, the screws 19 and 13 are removed and the main body is pulled from the auxiliary frame 7, and fixing plates 9 and 11.