An improved electrical trap construction for use in a high frequency circuit device, which is so arranged that a coaxial resonator is connected to a core pin of a coaxial connector mounted on a case which contains the device, so that main currents received from a hot signal line flow into or flow out of the coaxial resonator the inner conductive electrode layer of the coaxial resonator is in electrically conducting contact with the core pin of the connector so as to allow the coaxial resonator to provide parallel resonance at a frequency to be trapped.