A suction brush assembly for a vacuum cleaner capable of automatic height adjustment according to the present disclosure includes a suction brush body connected to a cleaner body at a rear side thereof and provided with a rotation brush for striking a surface to be cleaned to separate dirt from the surface to be cleaned at a bottom surface thereof; and an up/down adjusting unit for monitoring continuously a state of the surface to be cleaned and adjusting a height of the rotation brush body to vary a distance between the surface to be cleaned and the rotation brush according to the state of the surface to be cleaned so as to prevent the surface to be cleaned from being damaged by the rotating rotation brush.