This paper deals with a new slicing method of monocrystalline silicon ingot by wire EDM. In manufacturing process of silicon wafer, ID blade and multi wire saw have conventionally been used for slicing of ingot. However, it is difficult to apply these methods for larger ingot such as 12(R) or 16 " expected to be used in the near future, since there are some problems in efficiency, accuracy, slurry treatment, contamination and so on. Therefore, a new slicing method is required as soon as possible. In this study, the possibility of slicing by WEDM was proposed and the machining properties as well as surface integrity were experimentally investigated. It was made clear that WEDM had the possibility as a new slicing method and that contamination due to adhesion and diffusion of wire electrode material to machined surface could be reduced by using the reversed polarity WEDM.