To provide a crystal oscillator, in which a crystal resonator and an oscillation circuit can be subjected simultaneously to temperature control and which highly stabilizes frequency stability and can also be made small in size and light in weight, without using a metal block.

There is a plane that needs temperature control on an internal layer of a printed circuit board, where a heater 7 at which film resistance is formed is covered over the entire printed circuit board, facing the crystal resonator 1 and the oscillation circuit 5. A film resistance end being the heater 7 is connected to a temperature control circuit 6 through a through-hole because a transistor for temperature control supplies a heater current controlled by the control circuit 6 to the heater 7.