An oscillation circuits that provides stable oscillations even when the amount of phase rotation of a piezoelectric resonator is small or fluctuates. The oscillation circuit includes a first amplifier having an input and an output, and a piezoelectric resonator connected between the input and the output of the first amplifier. Moreover, the oscillation circuit feeds, back to the input, a current flowing from the output of the first amplifier to the piezoelectric resonator. The oscillation circuit further includes an alternating-voltage waveform shaping circuit that applies, to the piezoelectric resonator, an alternating-voltage waveform having rising portions sharper than those of a sine wave.