An apparatus as a tuning filter is provided for tuning the wavelength of a laser or a filter between extensive bandwidths, including a reflecting element, an optical system and a movable mount set up in the same optical path in order. The optical system focuses light on the reflecting element that induces dispersion effect. The reflecting element moves along an optical path as a spatial filter. The reflecting element is set up on the movable mount that moves along the optical path to push/pull the reflecting element and then to adjust the moving range of the reflecting element.