A wavelength filter includes a solid material that is optically transparent and including a pair of planar surfaces substantially parallel to each other; and a supporting member that supports the solid material on a planar surface of the solid material other than the pair of planar surfaces, the supporting member having a rigidity higher than that of the solid material. The solid material is a birefringent material of which an optical axis makes a predetermined angle with respect to a normal to the pair of planar surfaces, and the wavelength filter selects light having a wavelength that is determined by an optical length between the pair of planar surfaces by resonating the light between the pair of planar surfaces.