To provide a method of adjusting the output frequency in the condition of a finished product with a minimized space occupation by an output frequency adjusting resistor.

A temperature compensated crystal oscillator is composed of a crystal oscillator 103, a substrate 101 composed of a plurality of laminated substrates including an upper substrate with at least one component mounted thereon and a conductive pattern formed on at least one substrate, and a planar thin film resistor 109 formed on the upside of a lower substrate among the laminated substrates for adjusting the output frequency of the temperature-compensated crystal oscillator. Inserting the output frequency adjusting resistor between layers minimizes the space consumption to thereby miniaturize a final product. An output frequency adjusting method comprises a step of forming a temperature-compensated crystal oscillator having a planar thin film resistor formed on the upside of a lower substrate among a plurality of laminated substrates, and irradiating the bottom of the lower substrate with a laser beam to trim the thin film resistor, Thus, the output frequency is adjusted in the condition that the final product is finished and hence a more accurate room temperature output frequency is obtained.