PURPOSE: To obtain a miniature crystal oscillator which has a large temperature gain and a small change of oscillation frequency even with variation of the ambient temperatures, by forming a crystal oscillator and the 1st positive characteristic porcelain without directly contacting with the 2nd and 3rd positive characteristic porcelains and container.

CONSTITUTION: The 1st positive characteristic porcelain 2 is attached to a crystal oscillator in terms of conduction and heat transmission, and at the same time the 2nd positive characteristic porcelain 5 is attached to the bottom part 4 of a metallic container 3 storing the oscillator 1 and the porcelain 2 also in terms of conduction and heat transmission. Then the porcelains 2 and 5 are connected in series and electrically to each other. The 3rd positive characteristic porcelain 8 is attached to the cover part 7 of the container 3 in terms of conduction and heat transmission. This porcelain 8 is connected in parallel and electrically to the series circuit of porcelains 2 and 5. The oscillator 1 and the porcelain 2 are set so as to avoid a direct contact with the porcelains 5 and 8 as well as the container 3 to which those porcelains 5 and 8 are attached in terms of heat transmission. In such a constitution, it is possible to obtain a miniature crystal oscillator which has a large temperature gain and a small change of oscillation frequency even with variation of the ambient temperatures.