The Gd-Ni binary system has been reinvestigated by X-ray diffraction method and differential thermal analysis. The phase diagram has been determined. In this system, the following nine intermetallic compounds were found: Gd3Ni (decomposes at 735℃), Gd3Ni2 (decomposes at 690℃), GdNi (M. P. 1280℃) GdNi2 (decomposes at 1010℃), GdNi3(decomposes at 1110℃), Gd2Ni7(decomposes at 1200℃), GdNi4(decomposes at 1270℃), GdNi5(M. P. 1480℃) and Gd2Ni17(decomposes at 1285 ℃). Three eutectics occur: Gd3Ni-Gd3Ni2(635℃, ～32 at% Ni), GdNi2-GdNi2(880℃ ～56 at% Ni) and Gd2Ni17-Ni(1275℃, ～95 at Ni). Neither Go in Ni nor Ni in Gd shows any detectable solid solubility.