To provide a method for forming a picture having a subtle nuance such as a photograph on the surface of an aluminum alloy by applying a laser.

The method is provided with a laser machining stage where the surface of an aluminum alloy 1 is carved based on picture data, and an anode oxidation treatment stage where an anodically oxidized film 2 is formed on the surface of the aluminum alloy 1. In the laser machining stage, the carving depths (H11, H12 and H13) of a laser are controlled to provide the variation in the depth of the carving of the laser. Thus, the nuance of the picture can be represented on the surface of the aluminum alloy 1.