PURPOSE: To produce an Ni based alloy having excellent ductility at the ordinary temp. and high temp. by adding specific ratios of metallic elements such as B, Hf, etc., to the alloy consisted essentially of Ni and Al and formed the structure of Ni3Al as intermetallic compounds.

CONSTITUTION: The base metal 7 of the Ni based alloy contg., by atom., 75.4W79% Ni, 7W12% Al, 0.5W4% Hf, <0.5% B, <0.9% C, 4.5W11% Fe or Co and one or more kinds among the elements selected from the group of each ≤3% Mo, W, Nb, Ta, Zr and V and having the structure composed mainly of the intermetallic compound Ni3Al is charged to a crucible 6 made of alumina, is gradually descended in transparent quartz glass 1 provided with a heating element 5 made of carbon, is melted at the part of the exothermic body 5 and is gradually cooled at the part provided with glass fibers 4 of a heat-insulating material to turn the base metal into the alloy having a one way solidified structure in which crystals are grown downwards. By this method, the Ni based alloy having excellent ductility and strength at the ordinary temp. and high temp. of 400W800°C can be obtd.