There is provided a disk brake comprising: a piston that presses a brake pad to a disk rotor; and a caliper at which the piston is slidably provided through a piston seal, the caliper making the piston moved forward by hydraulic pressure, wherein the piston has that an anodized film layer formed by an anodized treatment is formed on a surface of a piston base body made of aluminum alloy, and a chromium plating layer is directly laminated on a surface of the anodized film layer.