PURPOSE: To improve the coupling between oscillations in flectional and torsional modes by properly setting the width, length, etc., of tuning fork arms of a quartz oscillator which oscillates with flectional and torsional modes coupled mutually.

CONSTITUTION: Tuning fork arms 1a and 1b of tuning fork type crystal 1 are provided with energizing electrodes 2∼17. Then, applying an AC voltage between electrode terminals A and B energizes the tertiary higher harmonic oscillation in the flectional mode and oscillation in torsional mode. In addition, when the tuning fork arm width is denoted as W, the length as L and the thickness as T, setting W2/LT between 0.09 and 0.21 improves the coupling between the oscillations in both the modes.