PURPOSE: To realize an automated working process and at the same time to improve the airtightness of a container of a rectangular piezoelectric oscillator, by forming projected parts at both sides of a place where an insulated substrate contacts with a cover and then melting and adhering those projected parts to each other to facilitate the assembling work of the container and a piezoelectric oscillating plate while is stored to the container.

CONSTITUTION: A depressed part 501 is formed on a main plane of one side of a rectangular insulated substrate 500 of thermoplastic resin, and lead terminals 200 and 300 are extended up to the cavity of the part 501 from both terminal faces in the lengthwise direction and fixed there. At the same time, exciting electrodes 102 and 103 and lead-out electrodes 104 and 105 are formed at both terminal faces and its both ends of a crystal oscillating plate 100 respectively. The plate 100 is set on the part 501 of the substrate 500, and the electrodes 104 and 105 are set on the terminals 200 and 300. In addition, a cover 600 is put over the opening part of the part 501. Then projected parts 603 and 508 are formed at both sides of a place where the substrate 500 contacts with the cover 600. These parts 603 and 508 are melted and adhered to each other. This facilitates the assembling work as well as to improve the airtightness of a container of a rectangular piezoelectric oscillator.