Abstract: A scroll housing structure of a multiblade blower suitable for lowering a collision noise of air and for preventing a flow loss. The structure comprises a scroll casing provided at its side wall with an air suction port, and an impeller provided in the scroll casing such that it is rotated by a rotational force of a drive source. The impeller has a plurality of blades arranged on its circumferential surface. The structure further includes an air guide unit for guiding air, expelled from the impeller, so as to prevent a streamline of the air from being curved and separated. The air guide unit extends along an upper inner surface of the scroll casing and initiates its extension from a position at which the streamline of the air expelled from the impeller is normally initially curved. Due to the air guide unit, the scroll housing structure of this invention reduces the collision noise of the air against the inner surface of the scroll casing and lowers the air flow loss.