To obtain a high-strength aluminum alloy for a motor frame which is excellent in heat radiation.

The aluminum alloy contains 0.2-1.0 wt.% Zr, 0.05-1.0 wt.% Si, at least one chosen from 0.02-0.1 wt.% Sn, 0.2-2.0 wt.% Cr, 0.02-0.15 wt.% In and 0.02-0.1 wt.% Ag, at least one chosen from 0.05-0.5 wt.% Mg, 0.05-0.5 wt.% Cu and 0.1-2.0 wt.% Ni, and the balance being aluminum. The aluminum alloy is yielded by casting the alloy in a mold and subjecting it to aging treatment at 300-450°C.