A piezoelectric bulk-wave resonator has a single-crystal LiNbO3 substrate whose Euler Angles are in the ranges of about (78° to 106°, 78° to 104°, 18° to 53°), a first driver electrode on a first main surface of the single-crystal LiNbO3 substrate, and a second driver electrode on a second main surface. The first driver electrode and the second driver electrode overlap with the single-crystal LiNbO3 substrate therebetween. The piezoelectric bulk-wave resonator uses the thickness-shear mode.