A voltage-controlled oscillator includes a piezoelectric element, a first package, an electronic element, and a second package. The first package contains the piezoelectric element. The second package contains the electronic element and the first package. The second package includes a base, and a lid. The electronic element and the first package are mounted in the base. The lid hermetically seals the electronic element and the first package together with the base. The base includes a substrate part, a first frame part, and a second frame part. The substrate part includes a first major face and a second major face opposite to the first face. The electronic element is mounted on the first major face. The first frame part includes a first frame face on which the first package is mounted. The first frame part is located on a peripheral edge of the first major face.