Abstract: A resonator 10 according to the present invention is provided with: an outer conductor 12 inside which a cavity 11 is formed; and an inner conductor 13 provided in the cavity 11 of the outer conductor 12. The inner conductor 13 includes: a movable body 133 provided to project into the cavity 11; a distal end portion 131 which is a separate member from the movable body 133 and which covers the distal end of the movable body 133, on the side of the movable body 133 that projects into the cavity 11; and a supporting rod 132 which is a rod-shaped member disposed inside the movable body 133, is provided with one end side fixed to the distal end portion 131 and the other end side fixed to the movable body 133, and which has a lower coefficient of thermal expansion than the movable body 133. By this means, it is possible to provide a resonator having a high temperature stability, which is applicable in multiple frequency bands, and a filter employing the resonator.