At present, the demand of hard and brittle materials (e. g. silicon and ceramics) is increasing with the development of electronics technology. The ID-blade which is one of the mechanical processing, has been used mainly in slicing silicon ingots. However silicon ingots become large due to the continuing imprvement of productivity and diminishment of production cost. It is difficult to use the ID-blade in slicing a large-size silicon ingot. Therefore, a wire tool with electrodeposited diamond grains that can slice such a silicon ingot has attracted attention. In this paper, the wire tool with electrodeposited diamond grains is fabricated by means of a nickel sulfamate bath and a copper pyrophosphate bath. Machining characteristics are examined through a series of slicing experiments, and material strength of the diamond wire tool is examined through theoretical and experimental results. This paper also discusses diamond wire tool life.