PURPOSE: To provide an optical filter device capable of obtaining a good cross talk characteristic without having dependency on polarization.

CONSTITUTION: A signal light is separated into a TM wave as a polarized wave A and a TE wave as a polarized wave B by a polarization beam splitter 34. Next, the polarized wave A is rotated by 45 degrees by a Faraday rotator 40 and rotated by 45 degrees by a polarized wave preserving fiber 72 to make it into the TE wave, and inputted to a filter 52. The polarized wave A separated by the filter 52 is reflected by a reflector 54, and inputted to the splitter 34. In the same way, the polarized wave B is rotated by 45 degrees by a Faraday rotator 42 and rotated by -45 degrees by a polarized wave preserving fiber 74 to make it into the TE wave, and inputted to a filter 68, and the separated polarized wave B is reflected by a reflector 70, and inputted to the splitter 34. And the separated polarized wave A and B are synthesized by the splitter 34 and made into a signal light, and this signal light is outputted to an optical device of a post stage.