A stripline filter that suppresses a fundamental wave frequency without increasing the size of a board and in which a harmonic frequency is easily set to a desired frequency. The stripline filter includes a glass layer having a relative dielectric constant lower than that of a dielectric board. A first top surface line is provided on a top surface of the dielectric board and has a resonant open end. A second top surface line and a side surface electrode are provided on the glass layer so as to extend from positions connected to the first top surface line.