A phase diagram of the alloys of the gadolinium-indium binary system was studied by differential thermal analysis, X-ray diffraction method and microscopic observation. The following six intermediate phases were verified: Gd3In,Gd2In,Gd5In3,Gdln,Gd2In3 and Gdln3. There are five eutectic transformations corresponding respectively to about 12 at % In (eutectic temperature 988℃), 30.5 at % In (1151℃), 38.5 at % In (1114℃), 64.5 at % In (1010℃). The eutectic on the In-rich side is degenerate. The decomposing temperature of the compound Gd2In3 formed by peritectie reaction is Tper= 1107℃. The periteetoid reaction 2Gd2+GdIn←→Gd5In3 occurs at 1071℃. Neither In in Gd nor Gd in In shows any detectable solid solubility.