In general, it is difficult to get pull in and pull out torque of a stepping motor directly by a 3-D dynamic magnetic field simulator, because it takes a lot of time to calculate. In this paper, we propose the simulation system which incorporates a behavior model of a stepping motor created by a 3-D static magnetic field simulator into a circuit simulator. By using this system, we can get pull in and pull out torque quickly. We compare the results of simulation with measured values. The results correspond with measured values well at low pulse rate. At high pulse rate, the results depend on a viscosity coefficient of the bearing and iron losses of stator.