Incremental Sheet Metal Forming (ISMF) is based on localized plastic deformation. In this process, a hemispherical-head tool, controlled by a CNC milling machine, shapes a sheet metal according to a defined path. Study of the forming force is one of the most important topics in this process. Increasing of vertical step size, tool diameter, wall angle and sheet thickness together with using of high strength sheet metals and lightweight alloys, leads to an increase in the forming force. In this paper, the performance of a novel forming process, named Ultrasonic Vibration assisted Incremental Sheet Metal Forming (UVaISMF) has been investigated. The procedure of design, manufacture and test of vibratory forming tool, is presented. The occurrence of longitudinal mode and resonance phenomenon has been confirmed by the results of modal analysis and experimental test. Furthermore, the effect of ultrasonic vibration on the vertical component of forming force and spring-back has been studied. Aluminium sheet of grade Al 1050-O is used as a work material. Experimental results obtained from straight groove test, indicate that ultrasonic excitation of forming tool, will reduce the average of vertical component of forming force and spring-back in comparison to conventional process.