A dust collector for a vacuum cleaner, comprising: a first cyclone installed within an outer case to filter out dust from air inhaled from an outside thereof and introduce the air from which dust has been filtered out into an inside thereof; a plurality of second cyclones accommodated in the inside of the first cyclone to separate fine dust from the air introduced to the inside of the first cyclone; a cover member disposed to cover an inlet of the second cyclone, wherein cyclones disposed adjacent to each other among the first and the second cyclones (110, 120) limit a first space within the first cyclone, and the cover member forms a second space communicating with the first space between the inlet and the cover member; a guide vane extended in a spiral shape along an inner circumference thereof and provided at the inlet to induce rotational flow in air introduced to an inside of each of the second cyclones through the first and the second space (S1, S2); a vortex finder provided at the center of each second cyclone and arranged to discharge air from which fine dust has been separated, wherein the guide vane is installed on the inlet between an inner circumference of the corresponding second cyclone and an outer circumference of the vortex finder, and the cover member comprises a communication hole corresponding to the vortex finder; and an upper cover disposed on the cover member to form a discharge passage so as to discharge air discharged through the communication hole to an outside of the dust collector, characterized in that the cover member further comprises a protrusion portion inserted into the vortex finder and provided with said communication hole. a first cyclone installed within an outer case to filter out dust from air inhaled from an outside thereof and introduce the air from which dust has been filtered out into an inside thereof; a plurality of second cyclones accommodated in the inside of the first cyclone to separate fine dust from the air introduced to the inside of the first cyclone; a cover member disposed to cover an inlet of the second cyclone, wherein cyclones disposed adjacent to each other among the first and the second cyclones (110, 120) limit a first space within the first cyclone, and the cover member forms a second space communicating with the first space between the inlet and the cover member; a guide vane extended in a spiral shape along an inner circumference thereof and provided at the inlet to induce rotational flow in air introduced to an inside of each of the second cyclones through the first and the second space (S1, S2); a vortex finder provided at the center of each second cyclone and arranged to discharge air from which fine dust has been separated, wherein the guide vane is installed on the inlet between an inner circumference of the corresponding second cyclone and an outer circumference of the vortex finder, and the cover member comprises a communication hole corresponding to the vortex finder; and an upper cover disposed on the cover member to form a discharge passage so as to discharge air discharged through the communication hole to an outside of the dust collector, characterized in that the cover member further comprises a protrusion portion inserted into the vortex finder and provided with said communication hole.