A magnetic roller includes a cylindrical magnetic field generation part (140), a cylindrical support part (143) that contacts both of the edges of the magnetic field generation part (140), further has a smaller diameter than the magnetic field generation part (140), and which is installed upon a common axis thereof as an axis of the cylindrical support part (143), and a depression part (140c) that is installed upon an obverse surface of the cylindrical magnetic field generation part (140), extends in a direction of the axis of the magnetic field generation part (140), and wherein a lengthwise magnet formation is inserted. The cylindrical magnetic field generation part (140) is configured of a main body portion (140a), which is installed upon a central portion of the cylindrical magnetic field generation part (140), and a reinforcing portion (140b), which is installed upon each of both ends, wherein the depression part (140c) is installed across the main body portion (140a) of the magnetic field generation part (140) overall, and the reinforcing portion (140b) is installed between an end of the depression part (140c) and an end of the support part.