A surface treatment method for roughening a surface of a metal material by a laser beam includes: forming a roughened surface adhesion portion on the surface of the metal material by irradiating the laser beam on the surface of the metal material to form a plurality of roughened regions within the roughened surface adhesion portion, each of the roughened regions being formed in a circular shape having an outer ring adjacent to each other. The roughened regions are arranged to satisfy the following Equation (1): 0.5a