Abstract: A filter device with transmission zeros is provided according to the present invention, which has an odd mode resonant frequency and an even mode resonant frequency. The filter device includes: a substrate, a metallic rectangular ring, a signal couple-in/couple-out module, and a metallic ground plane, wherein the surface of said metallic ground plane is parallel to the plane enclosed by said metallic rectangular ring, and said metallic rectangular ring applied to the filter device of the present invention has a perimeter shorter than or equal to the wavelength corresponding to the mean of said odd mode resonant frequency and said even mode resonant frequency, thereby allowing said filter device of the present invention, in a situation of specific bandpass frequency, to reduce its perimeter to about half of the perimeter of conventional annular rectangular dual mode filters.