In a crystal oscillator, a crystal resonator and an IC chip are hermetically sealed in a package. The crystal resonator includes: a crystal resonator plate including a first excitation electrode formed on a first main surface, and a second excitation electrode, which makes a pair with the first excitation electrode, formed on a second main surface; a first sealing member covering the first excitation electrode of the crystal resonator plate; and a second sealing member covering the second excitation electrode of the crystal resonator plate. A vibrating part including the first excitation electrode and the second excitation electrode of the crystal resonator plate is hermetically sealed by bonding the first sealing member to the crystal resonator plate, and the second sealing member to the crystal resonator plate.