A method of producing a magnet roll in which a magnetic property comparable to that obtained by an injection molding can be obtained in spite of an extrusion molding. According to a first embodiment, the yoke width of the magnetic-field extrusion die is varied along an extrusion direction. According to a second embodiment, a pipe filled with resin bonded magnet material is used as a shaft. According to a third embodiment, a shaft having a groove which is filled with magnet is used. According to a fourth embodiment, a shaft provided with surface magnetic charge is used. According to a fifth embodiment, a magnetized region of a shaft is set to be shorter than the length of a main magnet. According to a sixth embodiment, an extruded matter is moved while stored in a sizing metal mold having a magnetic circuit structure. According to a seventh embodiment, a sizing metal mold for storing an extruded matter therein is installed into a heating device and a cooling device equipped with a magnetic circuit structure while storing an extruded matter therein. According to an eighth embodiment, a preliminary magnetization is carried out with magnetic poles whose number is smaller than a finally-required number of magnetic poles, and then a re-magnetization is carried out with the finally-required number of magnetic poles.