PURPOSE: To get a high performance and low noise multi-vane blower, by fitting a nose-forming guide plate to the starting end of a spiral casing in accordance with the theoretical values of optimal nose position and angle and without regard to the size of its discharge port.

CONSTITUTION: A multi-vane blower is composed of a rotation shaft 1, impeller 2, suction nozzle 3, and spiral casing 4 for discharging air flow from the impeller 2. A thin guide plate 6 with a bent edge is fitted to the starting end 7 of spiral casing to form a nose 8 by the bent edge, its angle being selected within a range of 25° ≤ β ≤ 40°. This can improve the efficiency of the blower with reduced running noise.