The present invention provides a resonator and a filter that reduce the resonator radiation loss so as to achieve a high Q value that is inherent to a low-loss material while maintaining high power handling capability. In this manner, both high power handling capability and a high Q value can be achieved at the same time. The resonator is a microstripline structure and includes a line structure formed with resonance lines in which current standing waves are generated in a resonant state in a line, and currents in each two adjacent lines flow in the opposite directions from each other, and a connection line that connects the resonance lines at the portions having in-phase voltages among the nodes of the current standing waves of the resonance lines in the resonant state. The filter includes resonators of the same type as the above resonator.