An electroplated diamond tool is widely used for grinding, because of its high grinding efficiency. However, the height of the grain protrusion of the electroplated diamond tool is not uniform such that surface roughness deteriorates. Therefore, it is necessary to make the height of diamond grains uniform. In this paper, we propose a new electrical discharge truing (ED truing) method for the electroplated diamond tool. This ED truing method can be applied in a conventional electroplated diamond tool whose grains (diamond) have no electrical conductivity. As a result, it is shown that it is possible to truncate only the tips of diamond grains directly by this new ED truing method and to obtain an electroplated diamond tool with a uniform grain height. Moreover, it is confirmed that ground surface roughness is improved by using the ED-trued electroplated diamond tool.