A device for burnishing and smoothing metal parts, particularly suitable for use in mechanical-galvanic processes, comprising a main body having a fastening disc to which guides are radially coupled and the body of which includes at least three mobile propelling systems which are actuated by electro-mechanical means and move in a synchronized concentric manner, approaching and moving away from the central point and acting on a rotating frame from equidistant angles. The frame is configured to secure pieces to be treated and it also has a detachable head that is disposed centrally above a cylindrical tank. The propelling systems, provided with brushes, move from an open position in which they remain separate from one another and at a distance from the center, into a closed position in which they are joined to one another in the center of the tank, coming into contact with the structure containing the parts to be treated.