A resonator includes a shield conductor, a columnar body, and a first dielectric body. The shield conductor includes a first conductor located on a negative z-direction side and a second conductor located on a positive z-direction side, and has a cavity therein. The columnar body has a columnar shape, and is placed inside the cavity, an end in the negative z-direction thereof being joined to the first conductor, an interval being provided between an end in the positive z-direction of the columnar body and the shield conductor. The first dielectric body is placed inside the cavity, an end in the positive z-direction thereof being joined to the second conductor, an interval being provided between an end in the negative z-direction of the first dielectric body and the shield conductor, the first dielectric body surrounding the columnar body so as to be apart from each other.