As a small-diameter conductor for electric wires for automobiles, provided is an aluminum alloy wire satisfying all requests of sufficient strength, elongation and electroconductivity. The wire is an aluminum alloy wire including: magnesium; silicon; and aluminum and inevitable impurities as the balance, the content (M) by atomic percentage (at %) of the magnesium in the wire and the content (S) by atomic percentage (at %) of the silicon satisfying the following expressions (1) and (2), a metallic microstructure of a cross section of the wire having an average crystal grain size of 3 to 20 μm, a precipitation size of the metallic microstructure in the cross section being 100 nm or less, and the number density of the precipitations in the cross section being one or more per square micrometer. [Formula 1] 0.2≤M≤1.19  (1), and −0.81M+1.44≤S≤−1.54M+2.31  (2).