PURPOSE: To enable to easily adjust the rates of air circulation for respective rooms by a structure wherein normally closed type shutters, the degree of the opening of each of which is controlled by sliding a stopper, are provided at a plurality of suction ports in the ventilating device, which singly ventilates a plurality of rooms.

CONSTITUTION: When a centrifugal fan is rotated by a motor, the space formed by a casing encircling the centrifugal fan and an outer frame 4 encircling the casing is evacuated, resulting in tending the switching shutter 8 provided at the suction port 5 on the outer frame 4 to open inward. In this case, when a wing screw 12 is unscrewed and moved in a circular arc course with a supporting part 11 as a center, a buffer 10 arranged on the stopper 9 is lifted. Accordingly, the position, at which the buffer 10 abuts against said shutter 8, is changed, resulting in enabling to adjust the degree of opening of the shutter 8. Consequently, the opening area of the suction port 5 is changed, resulting in enabling to easily adjust the rate of air circulation by properly moving the position of the wing screw 12 so as to align with the air rate adjusting scale 14.