Abstract: There are provided: an aluminum alloy substrate for a magnetic disk, including 2.0 to 10.0 mass % (hereinafter, simply referred to as “%”) of Mg, 0.003 to 0.150% of Cu, 0.05 to 0.60% of Zn, 0.03 to 1.00% of Mn, and 0.00001 to 0.00200% of Be, as well as Fe restricted to 0.50% or less, Si restricted to 0.50% or less, Cr restricted to 0.30% or less, and Cl restricted to 0.005% or less, with the balance of Al and unavoidable impurities; and a method of producing the aluminum alloy substrate for a magnetic disk.