The purpose of this study is to make clear the machining effect of a new technique of cavitation aided machining (CAM) by which the workpiece can be easily finished in a fine surface with a very simple apparatus. The machining fluid, that is mixture of abrasive grains and water as carrier, is sucked by a pump, and the flow of machining fluid is controlled by a restrictor. Then the cavitation phenomenon locally occurs by the rapid decrease of carrier pressure, so that abrasive grains in the mixed fluid come to interfere on the surface. In this report, the possibility of applying CAM to precision machining is investigated by analyzing the surface finish, the stock removal and the behavior of carrier. Main conclusions obtained in this paper are as follows: (1) Action of abrasive grains onto the surface is induced by very fine cavitation impact caused by cavitation occurred in the lower part from the center of restrictor in a flow. (2) At 2.0mm in clearance, the cavitation impact of carrier becomes strongest, so that the stock removal and the decrease of surface roughness have maximum. (3) CAM can be applied to an ultraprecision machining by which the surface finish of Al-Mg alloy is improved from 7.3nm Ra with ultraprecision cutting down to the surface finish at 6.6nm Ra.