PURPOSE: To simplify the constitution and reduce the size of a high-frequency filter, by providing an input or output terminal inside the transmission line of a loop-like resonator.

CONSTITUTION: Split-ring resonators 11∼13 provided with capacities 11a∼13a for tuning frequency, capacitors 14 and 15 for coupling input-output, and input and output terminals 16 and 17, namely, coaxial connectors or pin terminals are provided. In such way, the input and output terminals are provided near the centers of two of the resonators 11∼13. Therefore, the box body of this filter can be miniaturized.