A centrifugal fan is provided. The centrifugal fan is configured such that an impeller having plural blades disposed between a disk-shaped main plate and an annular shroud along a circumferential direction is accommodated 5 in a casing, and that an air suctioned from a suction opening is discharged outward in a radial direction of the impeller by a centrifugal force due to a rotation of the impeller, and thereby discharging the air from the casing. The casing includes an upper plate, a lower plate, and plural supporting struts interposed between the upper plate and the lower plate, and 10 lateral sides of the casing have only the supporting struts to form a discharge opening.