PURPOSE:To miniaturize a switch, to attain the reduction in cost and to prevent the loss of the switch by providing an optical fiber type element which rotates the plane of polarization of incident light and a polarization beam splitter which branches and emits the light corresponding to the angle of the polarizing plane. CONSTITUTION:A polarization plane rotating element part 2 and an optical fiber type deflection beam splitter 5 are connected through a connection reinforcement part 4 and the polarization plane rotating element part 2 is provided with an electromagnet 10 such as a coil on a polarization plane rotating element 8 by holding a buffer layer 9 therebetween. The polarization plane rotating element 8 being a Faraday rotator is constituted by using a glass which has a large Verdet's constant for a core part, fitting a clad part made of, for example, silica or germanium externally to the core, and sintering and drawing them. In this case, the specific refractive index difference of a fiber is equalized to the specific refractive index difference of the deflection beam splitter 5 which is connected thereafter to reduce the connection loss. Consequently, signal light is emitted from a projection terminal 6 when a magnetic field is applied and from a projection terminal 7 when not, so the function of the optical switch is obtained.