A piezoelectric resonator includes a laminated thin film having a first thin film portion supported by a substrate and a second thin film portion spaced apart from a first main surface of the substrate and acoustically isolated from the substrate. The second thin film portion of the laminated thin film includes a piezoelectric thin film, a first electrode disposed on the upper surface of the piezoelectric thin film, and a second electrode disposed on the lower surface of the piezoelectric thin film and being larger and thicker than the first electrode. The piezoelectric resonator further includes a mass adding film disposed around the first electrode and on at least one portion of a region extending outward from the periphery of a piezoelectric vibrating portion at which the first and second electrodes overlap each other with the piezoelectric thin film disposed therebetween. The second electrode arranged so as to extend beyond the piezoelectric vibrating portion to a region at which the mass adding film is disposed.