The present invention is one where, in a lead wire led-out type crystal oscillator of constant temperature type for high stability, comprising: a heat supply body that supplies heat to a crystal resonator from which a plurality of lead wires are led out, to maintain the temperature constant; an oscillating element that constitutes an oscillating circuit together with the crystal resonator; a temperature control element that constitutes a temperature control circuit for controlling the temperature of the crystal resonator; and a circuit board for mounting the heat supply body, the oscillating element, and the temperature control element, and through which lead wires of the crystal resonator are passed through for mounting, the heat supply body comprises: a heat conducting plate which has through-holes for the lead wires and is mounted on the circuit board, and which faces, and is directly thermally joined to, the crystal resonator; and a chip resistor for heating which is mounted on the circuit board adjacent to the heat conducting plate, and is thermally joined to the heat conducting plate. As a result, a lead wire led-out type crystal oscillator of constant temperature type for high stability wherein the structure is simplified, and in particular the height dimension is reduced can be provided. Moreover, the present invention is a constant temperature type surface mounting type crystal oscillator which uses a crystal resonator for surface mounting which is mounted on the circuit board together with the oscillating elements and temperature control elements, and is constructed such that the crystal resonator is arranged on a ceramic substrate, and at least a chip resistor for heat generation and a highly temperature-dependent highly heat sensitive element are arranged on the ceramic substrate. The structure is such that the crystal resonator is arranged on one principal plane of the ceramic substrate, and the chip resistor and the temperature sensitive element are arranged on the other principal plane of the ceramic substrate, and the other principal plane of the ceramic substrate is positioned facing one principal plane of the circuit board, and heat conductive resin is interposed between the chip resistor and the circuit board. A surface mounted crystal oscillator of constant temperature type in which miniaturization is advanced, and the structure is simplified, is provided.