A polygon scanner has a lighter rotating shaft on which a polygon mirror is mounted, to prevent a positional deviation of the polygon mirror from the rotating shaft in high speed rotation, in which the rotating shaft is supported through a dynamic pressure air bearing on a fixed shaft, in which the polygon mirror and motor constituent members are mounted on the rotating shaft, and in which the rotating shaft and the polygon mirror are made of respective light weight materials matched with each other in coefficient of thermal expansion, for example of aluminum or an aluminum alloy. Further, an anodic oxide film is formed at least on a portion where the rotating shaft could contact with the fixed shaft, and floating means is provided for constantly floating the rotating shaft relative to the fixed shaft upward in an axial direction thereof. A process for producing the polygon scanner comprises making a predetermined masking on a portion where the rotating shaft could contact with the fixed shaft, prior to an anodic oxidation treatment to form an anodic oxide film on the portion, and then performing the anodic oxidation treatment, whereby, during the treatment, forming an anodic oxide film and a pattern of recesses and protrusions for dynamic pressure generation corresponding to a pattern of the masking, which are constituent elements of a dynamic pressure air bearing.