To provide an angle adjusting device for an optical filter which can rotate the optical filter in a state being stable so as to change the light incident angle to the optical filter.

The angle adjusting device for the optical filter has a fitting member 26 fixed to one end part of the optical filter 7, a supporting member 27 which is fixed to the other end part of the optical filter 7 and is rotatably supported on a base, an angle adjusting member 28 which is fitted to the member 26 and/or the member 27 and rotates the optical filter 7 on the base, and an angle control part 29 which controls the rotation angle of the member 28 so that the light incident angle to the optical filter 7 can be the desired angle.