A new route for synthesizing GaN from gallium metal by grinding in NH3 gas atmosphere is proposed in this paper. The proposed route is to grind Ga metal under ammonia gas atmosphere by using a planetary mill with unisized ZrO2 balls. The grinding, which induces mechanochemical reaction between the two, has been conducted. The formation of GaN was confirmed in XRD patterns, and the peak intensity of GaN increases with grinding time.