The deformation of microstructures by the application of magnetic fields is one of the effective methods for controlling microstructures. We attempt to employ magnetic particles and an elastic material to fabricate a new micro device without electric wiring. It is essential to understand how magnetic force works to the micro particle for designing a new micro actuator device. Theoretical formulation is proposed and used to express magnetic effect and deformation of the elastic material. We also develop a computational system to simulate this actuator.