A magnetic tunnel junction device and a manufacturing method therefor are provided. The magnetic tunnel junction device comprises: a seed layer having an FCC (001) crystal structure; a first ferromagnetic layer located on the seed layer and having perpendicular magnetic anisotropy; a tunneling barrier layer located on the first ferromagnetic layer; and a second ferromagnetic layer located on the tunneling barrier layer and having perpendicular magnetic anisotropy, wherein the first ferromagnetic layer has a BCC (001) crystal structure and does not have boron. Therefore, the magnetic tunnel junction device, which is structurally and thermally more stable, can be provided by using the seed layer configured to assist the crystal growth of a boron-free magnetic layer in a BCC (001) direction and provide perpendicular magnetic anisotropy thereto, that is, W2N or TaN which is a nitrogen-doped metal material having a cubic crystal structure and having a similar lattice constant to that of a magnetic layer material.