PURPOSE: To produce a composite magnet material, in which a metallic material easy to work is firmly bonded to an MnAlC-based magnet alloy material difficult to work, with high productivity.

CONSTITUTION: A powdery material 13 obtained by gas-atomizing an MnAlC- based magnet alloy and a core 12 consisting of the same material as an encapsulating material are placed in a capsule 11 made of the MnNiCu-based alloy or FeMnNi-based alloy easy to work, and the aggregate as a billet 16 is hot or warm-extruded to obtain an extrusion product 20. In the extrusion product 20, an outer layer 21 and a core 22 are integrally bonded to the intermediate layer 23 of a densified magnetic alloy transferred from the powdery material through an alloy layer by diffusion.