A molding device for molding a magnet roll with a profiled cross-section comprises a heating and kneading unit that supplies, to a cylindrical metal mold, a kneaded material obtained by heating and kneading a raw mixture including ferromagnetic particles and thermoplastic resin, an extrusion molding unit that molds the supplied kneaded material by the metal mold, and a magnetic field generating unit disposed at an end portion of the metal mold in a lengthwise direction that generates a magnetic field inside the metal mold, and the metal mold has a profiled C-shaped cross-section at an inlet for the kneaded material and a profiled cross-section at an outlet for the kneaded material more complex than the inlet.