To produce a hard Al alloy sheet excellent in DI workability by minimal stages at a low cost by subjecting a molten Al alloy of specific composition to continuous casting and rolling into a sheet by means of a twin-roll caster and then applying heat treatment, cold rolling, and annealing under respectively specified conditions.

A molten Al alloy, having a composition containing, by weight, 0.5-2.5% Mg, 0.5-2.5% Mn, 0.1-0.7% Fe, 0.05-0.5% Si and 0.005-0.20% Ti independently or in combination with 0.0001-0.05% B and further containing one or ≥2 kinds among small amounts of Cu, Cr, and Zr, is solidified by means of a twin-roll caster at ≥50°C/sec solidification rate and then continuously cast and rolled into a sheet of 1-4mm thick under a load of ≥50kgf per millimeter of width. Subsequently, the sheet is held at 580-630°C for ≥6hr and then held at 480-530°C for 1hr. The sheet is cold-rolled at 50-95% rolling rate and then subjected to process annealing at 380-600°C for ≤2min and to finish annealing at 100-150°C for ≤8hr.