To solve a problem of not being able to cope with the higher speed and higher image quality of a recent full-color machine since high magnetic flux density cannot be secured inexpensively in a conventional cylindrical magnet roller due to the securing of the high magnetic flux density by using an expensive rare earth based magnet block and the imbedding of the same in a groove in the axial direction of the cylindrical magnet.

The cylindrical magnet which is formed by molding a mixture mainly composed of ferromagnetic powder and a resin binder has the cylindrical magnet imbedded with a plurality of numbers of magnet pieces that are repulsed magnetically from each other in an indention in an outer periphery section.