A high strength aluminum alloy is expressed by a general formula, Al.sub.a X.sub.b Mm.sub.c, in which "X" stands for at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zr, "Mm" stands for a misch metal, a content "a" of aluminum falls in a range of from 95.2 to 97.5 atomic %, and a content "b" of "X" and a content "c" of the "Mm" fall in a hatched area enclosed by points "A," "B," "C" and "D" of accompanying FIG. 1 on atomic % basis, and whose metallic phase includes microcrystalline phases or mixed phases containing amorphous phases in a volume content of less than 50% and the balance of microcrystalline phases. As a result, the amorphous phases or the microcrystalline phases are dispersed uniformly in its base microcrystalline phases appropriately, and at the same time the thus generating base microcrystalline phases are reinforced by forming solid solutions including the "Mm" and the transition metal element "X" as well. Hence, the high strength aluminum alloy comes to have a low specific gravity and a high strength which have not been available from conventional Al amorphous alloys.