PURPOSE: To peel off substrates from each other or a substrate from a spacer easily by correction annealing of an aluminum alloy substrate for magnetic disk.

CONSTITUTION: In a manufacture of an aluminum alloy substrate for magnetic disk containing 3.0-7.0wt.% Mg, an oxide film is formed on the surface of the aluminum alloy by pre-treatment when performing correction annealing of the aluminum alloy. Washing in hot water or anode oxidation is desirable as an oxide layer formation means. It is desirable that the oxide layer after pre- treatment should be 100 or longer but should be 1μm or less in terms of grinding property of the post-process.