A dust collector for a vacuum cleaner, comprising: a first cyclone provided within an outer case to filter out dust from air introduced from an outside of the outer case; and at least one second cyclone accommodated inside of the first cyclone to form a first space between the first cyclone and the at least one second cyclone, wherein the at least one second cyclone is configured to separate fine dust from the air introduced to the inside of the first cyclone; wherein the at least one second cyclone includes: a cylindrically shaped casing having a first outlet (120b1) formed on an outer circumference of a lower side of the casing to discharge fine dust in an outer circumferential direction of the casing; a vortex finder provided in the center of an upper portion of the casing to discharge air from which fine dust has been separated; at least one guide vane spirally extended along an inner circumference of the at least one second cyclone to induce rotational flow of the air introduced to an inside of the casing of the at least one second cyclone through an inlet of the second cyclone via the first space, wherein the at least one guide vane is integrally provided on the at least one second cyclone; and a cover forming a bottom surface of the casing mounted at a lower portion of the casing and having a discharge pipe provided at a center of the cover, wherein the discharge pipe is formed with a second outlet (120b2) to discharge fine dust in a downward direction of the casing. a first cyclone provided within an outer case to filter out dust from air introduced from an outside of the outer case; and at least one second cyclone accommodated inside of the first cyclone to form a first space between the first cyclone and the at least one second cyclone, wherein the at least one second cyclone is configured to separate fine dust from the air introduced to the inside of the first cyclone; wherein the at least one second cyclone includes: a cylindrically shaped casing having a first outlet (120b1) formed on an outer circumference of a lower side of the casing to discharge fine dust in an outer circumferential direction of the casing; a vortex finder provided in the center of an upper portion of the casing to discharge air from which fine dust has been separated; at least one guide vane spirally extended along an inner circumference of the at least one second cyclone to induce rotational flow of the air introduced to an inside of the casing of the at least one second cyclone through an inlet of the second cyclone via the first space, wherein the at least one guide vane is integrally provided on the at least one second cyclone; and a cover forming a bottom surface of the casing mounted at a lower portion of the casing and having a discharge pipe provided at a center of the cover, wherein the discharge pipe is formed with a second outlet (120b2) to discharge fine dust in a downward direction of the casing. a cylindrically shaped casing having a first outlet (120b1) formed on an outer circumference of a lower side of the casing to discharge fine dust in an outer circumferential direction of the casing; a vortex finder provided in the center of an upper portion of the casing to discharge air from which fine dust has been separated; at least one guide vane spirally extended along an inner circumference of the at least one second cyclone to induce rotational flow of the air introduced to an inside of the casing of the at least one second cyclone through an inlet of the second cyclone via the first space, wherein the at least one guide vane is integrally provided on the at least one second cyclone; and a cover forming a bottom surface of the casing mounted at a lower portion of the casing and having a discharge pipe provided at a center of the cover, wherein the discharge pipe is formed with a second outlet (120b2) to discharge fine dust in a downward direction of the casing.