A device for treating or acting on workpiece surfaces by means of an actuator, such as a cutting or engraving laser or a nozzle for applying oils, paints, adhesives, dyes, or etchants is disclosed. An ultrasonic levitation force field is generated by means of a sonotrode, which is coupled to the actuator into a working unit, such that the movably suspended working unit is supported on the workpiece surface in a hovering manner. The ultrasonic levitation force field allows a highly precise positioning of the working unit relative to the workpiece surface so as to allow a precise treatment or machining of the workpiece surface.