PURPOSE: To realize a microstrip line resonator used for an oscillator for several hundreds MHz - several GHz and a resonator for a filter or the like in which the difficulty in the correction of the resonance frequency is solved and the resonance frequency is adjusted with high accuracy and less man-hour.

CONSTITUTION: The resonator is provided with a microstrip line 2 formed on a dielectric base 1, a conductor pattern 4 formed on the face of the dielectric base 1 opposite to the microstrip line 2, and throughhole wiring 6a, 6b connecting the microstrip line 2 and the conductor pattern 4 in parallel. Thus, when the microstrip line 2 is trimmed, the resonance is adjusted with less man- hour and high accuracy without rapid increase in the resonance frequency change per unit trimming when the microstrip line 2 is trimmed.