A multi-cyclone dust separator is provided, including a first cyclone unit that centrifugally separates dust from dust-laden air drawn into the first cyclone unit through a first air inlet, and a second cyclone unit that is formed inside the first cyclone unit, wherein the second cyclone unit includes a second cyclone body that has a second air inlet through which the air, from which the dust is separated by the first cyclone unit, enters the second cyclone body, and a guide unit that enables the air entering the second cyclone unit to be rotated.