To provide a magnet roller which has rearcely warp, high strength and excellent magnetic characteristic, and a manufacturing method of the roller.

In this magnet roller, an axial part 3 is protruded and formed on one end side of a roller part 2. Specifically, melted resin magnetic material is injected in a mold from the axial part 3 side, and the roller part 2 and axial parts 3, 4 are molded in an unified body. The magnet roller formed by the above process is so constituted that a ratio (D/d1) of a diameter D of the roller part 2 to a diameter d1 of the axial part 3 satisfies the following inequality, 1≤D/d1≤2.4.