An apparatus for adjusting a height of a suction brush for use in a vacuum cleaner includes a height adjusting knob rotatably disposed in an inserting recess formed in the suction brush, and having an inclined part formed thereon, so that a height of the suction brush from a surface to be cleaned is varied as a position of the height adjusting knob rotated, a supporting member to support the suction brush in contact with the inclined part thus to allow the suction brush to be ascended and descended by the inclined part, and a passage disposed between an inner circumferential surface of the inserting recess and an outer circumferential surface of the height adjusting knob to pass fine dirt therethrough. With the passage, the fine dirt is not tied up between the inner circumferential surface of the inserting recess and the outer circumferential surface of the height adjusting knob. Accordingly, the rotation of the height adjusting knob is not restricted or obstructed due to the fine dirt.