The invention discloses a metal sheet reinforcement method which comprises the following steps: (a) providing a metal sheet, wherein the metal sheet is provided with a first surface and a second surface which are opposite to each other; (b) stamping a plurality of first protruding parts protruding from the first surface on the metal sheet to form a stamping region; (c) stamping the first protruding parts respectively to form a plurality of second protruding parts protruding from the second surface respectively; (d) flattening the second protruding parts to recover the metal sheet.