The suction unit comprises: a cover having an air inlet; a noise reduction part provided in the cover, arranged outside the air inlet and spaced therefrom; an impeller for flowing the air which has passed through the noise reduction part and then the air inlet; a motor having a rotating shaft connected to the impeller; a guide apparatus for guiding the flow of the air which has flown from the exit of the impeller; and a shaft coupling part coupled to the rotating shaft connected to the impeller.