PROBLEM TO BE SOLVED: To obtain an oscillator circuit which drastically reduces oscillation rise time and gets an oscillation output just after oscillation start. SOLUTION: A short-circuiting means 7 is placed side by side as an input terminal voltage biasing means of an inverting amplifier 1 between its input and output terminals, also, an output buffer circuit which receives an output of the amplifier 1 and performs an oscillation output always amplifies a minute amplitude output of the amplifier 1, the amplifier 1 is activated at the time of oscillation start, also, a vibrator 5 is excited by giving potential difference to both ends of the vibrator 5 and the intra-input-output terminal of the amplifier 1 is short-circuited by thereafter operating the means 7 in a prescribed period. Thus, because resonance current peak in the vibrator 5 is increased and minute vibrations of the vibrator 5 are promoted, it is possible to perform oscillation start at an early stage.