A crystal oscillator internally includes a package storing a crystal unit. The crystal oscillator is configured to include: a substrate having one surface side on which the crystal unit is disposed and another surface side on which a circuit component and a heating element are disposed, the circuit component including an oscillator circuit that oscillates the crystal unit, and the heating element regulating a temperature inside the package; a stepped portion formed at an inner wall of the package to support only an end portion of the substrate from the one surface side such that the crystal unit, the circuit component, and the heating element are spaced from a wall portion of the package; and a wire that connects between a terminal disposed at the heating element and a terminal disposed inside the package without via the substrate.