PURPOSE: To reduce the manufacture man power for a blower system by forming two ventilation passages by the partition provided in a double suction type multiblade blower in order to simplify the ventilation passage.

CONSTITUTION: An impeller (A) is so constructed that a blade 3 is disposed circumferentially between a core plate 1 and a side plate 2. Said impeller (A) is disposed within a spiral casing (B) in which the blowing directions of the forward casing (a) and the rearward casing (b) are different. By forming each independent ventilation passage in the forward and rearward side of said core plate 1 acting as a boundary, the partitions (c), (d) disposed in the casing (B) is formed in such a manner that the passages are maintained sufficiently in a tightly closed state. When said motor (C) is driven to rotate said impeller (A), the air flows from an indoor side heat exchanger 5 to a blow-off port so far as the indoor side and it is blown up from an outdoor side heat exchanger 6 to a compressor 7 so far as the outdoor side.