A multirole circuit element, comprising: a first transmission line connected at one end thereof to an input line and at another end to an output line; a second transmission line having an electrical length equal to an electrical length of said first transmission line connected at one end thereof to said input line and at another end to said output line; and one or more switch circuits each connected to either said first transmission line or said second transmission line, wherein the characteristic impedance for the even mode of said first transmission line is equal to the characteristic impedance for the even mode of said second transmission line, and the characteristic impedance for the odd mode of said first transmission line is equal to the characteristic impedance for the odd mode of said second transmission line, characterized in that: a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said first transmission line are uniform in a length direction of said first transmission line, and a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said second transmission line are uniform in a length direction of said second transmission line, so that the multirole circuit element is capable of selectively operating as any of at least a resonator and a transmission line depending on an on/off state of said switch circuits. a first transmission line connected at one end thereof to an input line and at another end to an output line; a second transmission line having an electrical length equal to an electrical length of said first transmission line connected at one end thereof to said input line and at another end to said output line; and one or more switch circuits each connected to either said first transmission line or said second transmission line, wherein the characteristic impedance for the even mode of said first transmission line is equal to the characteristic impedance for the even mode of said second transmission line, and the characteristic impedance for the odd mode of said first transmission line is equal to the characteristic impedance for the odd mode of said second transmission line, characterized in that: a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said first transmission line are uniform in a length direction of said first transmission line, and a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said second transmission line are uniform in a length direction of said second transmission line, so that the multirole circuit element is capable of selectively operating as any of at least a resonator and a transmission line depending on an on/off state of said switch circuits. a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said first transmission line are uniform in a length direction of said first transmission line, and a characteristic impedance for an even mode and a characteristic impedance for an odd mode of said second transmission line are uniform in a length direction of said second transmission line, so that the multirole circuit element is capable of selectively operating as any of at least a resonator and a transmission line depending on an on/off state of said switch circuits.