A lot of studies on the ultra-precision cutting of single crystal silicon have been reported and they used the single crystal diamond cutting tools having the sharp cutting edge. However, the diamond cutting tools having small chamfer at the cutting edge are usually used in practical machining shops. In addition, studies on the relationship between the tool wear and the machined surface have been reported little although the relationship is important in practical applications. In this study, ultra-precision cutting of single crystal silicon, using cutting fluids, feed rate, and depth of cut as experimental parameters, were carried out by using the single crystal diamond cutting tools having small chamfer and large nose radius, and effects of the cutting fluids, the feed rate, and the depth of cut on the machining accuracy and tool wear were studied. As a result, the optimum cutting conditions was obtained as follows: the cutting fluid was kerosene, the feed rate was 2.0μm/rev, and the depth of cut was 1.0μm.