This paper describes the numerical simulation of the dynamic behavior of a ferromagnetic thin plate vibration in a magnetic field. The behavior of a ferromagnetic cantilevered plate, which is set in the direction of uniform magnetic field, shows that its natural frequency increases with the external magnetic induction. Two methods were applied to evaluate this phenomenon. The magnetic field of the deformed shape has been analyzed by 3D analysis and ID approximation. The natural frequencies were evaluated by the energy method in 3D case and by a transient response in ID case. The results show that the natural frequency change can be explained by the magnetic stiffness effect caused by magnetization including its saturation. (ci 1996 IEEE.