Abstract: In electroplating aluminum on a metal sheet with use of a molten salt bath comprised of from 40 to 80 mol % of an aluminum halide and from 20 to 60 mol % of an N-alkylpyridinium halide, or a molten salt bath obtained by mixing an organic solvent in said first-mentioned bath, said metal sheet is activated to improve deposit adhesion by carrying out, before plating, electrolysis on said metal sheet, bringing it to serve as an anode and with use of an activating bath having the same composition as said molten salt bath. Also, the bath is purified by leaving metallic aluminum immersed in the bath, or by carrying out preliminary electrolysis under a current density of 0.5 A/dm.sup.2 or less with immersion of an anode and a cathode both made of metallic aluminum in the molten salt bath.