A constant-temperature type crystal oscillator includes: a surface-mount crystal unit, in which a crystal element is housed in a case main body to hermetically encapsulate the crystal element with a metal cover, and which includes a crystal terminal serving as a mounting terminal that is electrically connected to at least the crystal element on an outer bottom face of the case main body; a thermistor that detects an operational temperature of the surface-mount crystal unit; and a circuit substrate, on which elements forming an oscillator circuit and elements forming a temperature control circuit along with the thermistor are installed. The thermistor includes a first and second terminal electrode and a temperature detecting electrode that is electrically independent of the first and second terminal electrode. The temperature detecting electrode is electrically connected to the crystal terminal of the surface-mount crystal unit through a circuit pattern formed on the circuit substrate.