To optimize a multi-pole magnet roller a finite element method with Genetic algorithm is carried out. A multi-pole magnet roller recently used in the development system of the electrophotography, such as copiers, or laser printers. One procedure for producing the magnet roller is the extrusion molding with applying magnetic fields to the material. This scheme forms magnetic characteristics or flux density pattern by controlling to apply magnetic fields. For desired magnetic characteristics, we must adjust various parameters such as a shape of dies and current in the coils, but the fabrication required many efforts and resources. To make this process more efficient, a FEM simulation tool for the molding process has been developed. And Genetic algorism, which can optimize many parameters, is acquitted to decide these parameters. Then a high flux magnetic density at the main pole can be obtained in comparatively shorter fabrication time than the past.