This paper deals with a numerical modeling of nonlinear magnetic properties of ferromagnetic shape memory alloys (FSMAs). In order to design new magnetic actuators by using the FSMAs, it is necessary to develop an effective engineering modeling, which can represent the nonlinear magnetic properties depending on stress and temperature. This paper presents measured relationship among stress, temperature and magnetic properties of a Fe-based FSMA. On the basis of the measured result, we have developed a numerical modeling with an arc-tangent function. The modeling is applied to analyze a simple example for verification and the calculated results demonstrate its applicability in numerical simulations.