A filter cylinder having a dust cleaning device of a dust collector is provided. The filter cylinder has a cylindrical outer frame. An HEPA filter is provided inside the filter cylinder. The inner wall of the filter is provided with a collar. A cleaning device is disposed in the filter cylinder. The cleaning device includes a bracket. Two ends of the bracket are each provided with a flap member corresponding to the inner wall of the collar. The cleaning device is rotatable in the filter cylinder, with the flap member to flap the collar and further to vibrate the filter, so that the dust adsorbed to the filter drops from the filter to enhance the structural strength of the filter and to prolong the service life of the filter.