The present invention provides an Al—Mg series alloy sheet of high-Mg with improved press formability and homogeneity which can be applied to automobile outer panels and inner panels. This is an Al—Mg series aluminum alloy sheet having 3.5 to 3 mm in thickness cast by twin-roll continuous casting and cold rolled, comprising over 8% but not more than 14% Mg, 1.0% or less Fe, and 3.5% or less Si with the remainder being Al and unavoidable impurities wherein the mean conductivity of the aluminum alloy sheet is in the range of at least 20 IACS % but less than 26 IACS %, the strength-ductility balance (tensile strength×total elongation) as a material property of the aluminum alloy sheet is 11000 (MPa %) or more, and the homogeneity and press formability of the sheet have been improved.