An oscillator includes: a substrate; a reference oscillation circuit including a first MEMS oscillator disposed above the substrate, the reference oscillation circuit outputting a first oscillation signal; at least one voltage-controlled oscillation circuit including a second MEMS oscillator disposed above the substrate, the oscillation frequency of the at least one voltage-controlled oscillation circuit being controlled based on a control signal, the at least one voltage-controlled oscillation circuit outputting a second oscillation signal; a frequency division circuit dividing the frequency of the second oscillation signal and outputting a frequency division signal; and a phase-comparison circuit outputting the control signal based on a phase difference between the frequency division signal and the first oscillation signal, wherein the first MEMS oscillator and the second MEMS oscillator each have a first electrode and a second electrode, the second electrode has a movable part disposed so as to face the first electrode.