PURPOSE: To obtain an oscillation circuit for flowmeters which can perform pertinent self-excitation oscillation by using a ceramic vibrating element as an ultrasonic vibrating element.

CONSTITUTION: A resistor 15 for feedback and capacitor 20 for feedback are connected in parallel between the in-phase input terminal 11b and output terminal 11c of an operational amplifier 11. Since the capacitor 20 is connected in parallel with the resistor 15, the phase lag quantity of the output signal of the title oscillation circuit caused by an ultrasonic vibrating element 4 for transmission is canceled by means of the capacitor 20 at a frequency near a resonance point fs and the output signal of the oscillation circuit is inverted in phase. Therefore, even when a ceramic vibrator having a small Q-value is used as the element 5, the element 5 can make self-excitation oscillation at the frequency near the resonance point fs in an induced component area M and a high transmitting efficiency can be obtained.