A piezoelectric oscillator comprises an oscillation stage (2) for generating pulses by exciting a piezoelectric resonator; and an output stage (13) for amplifying the pulses and outputting the amplified pulses. Start delay means responsive to electric power to the oscillator being turned on is provided for delaying the start of operation of the output stage (13) relative to that of the oscillation stage (2) by a delay time selected from a plurality of available delay times. Thus, the start characteristics of the oscillator are improved by reducing power noise being generated during a transient period after the power supply has been switched on.