A vacuum cleaner having an improved structure capable of enhancing suction performance includes a suction unit provided in a main body, the suction unit including an impeller disposed to suck air by rotating about an axis thereof, and a diffuser disposed to guide air discharged from the impeller. The diffuser includes an inner casing, an outer casing disposed to be spaced apart from an outer circumference of the inner casing and to form a path through which the air discharged from the impeller flows, and a plurality of vanes disposed at the inner casing to guide the air discharged from the impeller to the path, and the plurality of vanes protrude toward the outer casing to cross at least a part of the path.