A high-strength and high-toughness aluminum-based alloy having a composition represented by the general formula: Al.sub.a Ni.sub.b X.sub.c M.sub.d Q.sub.e, wherein X is at least one element selected from the group consisting of La, Ce, Mm, Ti and Zr; M is at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Y, Nb, Mo, Hf, Ta and W; Q is at least one element selected from the group consisting of Mg, Si, Cu and Zn; and a, b, c, d and e are, in atomic percentage, 83.ltoreq.a.ltoreq.94,3, 5.ltoreq.b.ltoreq.10, 0.5.ltoreq.c.ltoreq.3, 0.1.ltoreq.d.ltoreq.2, and 0.1.ltoreq.e.ltoreq.2. The aluminum-based alloy has a high strength and an excellent toughness and can maintain the excellent characteristics provided by a quench solidification process even when subjected to thermal influence at the time of working. In addition, it can provide an alloy material having a high specific strength by virtue of minimized amounts of elements having a high specific gravity to be added to the alloy.