PURPOSE: To manufacture an Al alloy having superior strength and corrosion resistance and suitable especially for use as the material of a plate by specifying the composition of an alloy consisting of Si, Mg, Zn, Mn, Sn and Al and by regulating conditions during rolling and heat treatment.

CONSTITUTION: An alloy consisting of 2.3W3.5% Si, 0.4W1.0%Mg, 0.05W0.5% Zn, 0.4W0.9% Mn, 0.01W0.06% Sn and the bakance Al with impurities is homogenized at 400W560°C for 1W24hr, hot-rolled at 400W540°C, cold-rolled at >50% draft, and subjected to soln. heat treatment. Si, Mg, Zn, and Sn as the added components increase the strength of the alloy, and Sn enhances the correction resistance furthermore. The homogenizing treatment accelerates the solubilization of Mg, Zn, Si, etc. and the precipitation of a finely divided Mn compound, and under said rolling conditions the cast structure and the hot-rolled structure are destroyed to obtain the required strength.