This paper presents the development of the optical switch using magnetic behavior of magnetic fluids, which is expected to be used broadly in high-speed information communication. The magnetic fluids for switching an incident light, have the magnetic characteristics of magnetic materials and fluidity of liquids, simultaneously. The relations are derived between the intensity of magnetic field and the angle of optical fiber which is bent by a behavior of magnetic fluid when the magnetic field is applied. When optical switch is implemented by the movement of liquid using magnetic fluid, the existing problem of durability for optical switch will be improved. Thus, this study shows the feasibility of the application for the optical switches using magnetic fluids.