An oscillator includes a front side voltage divider, a rear side voltage divider, and an oscillation unit. The front side voltage divider includes a first resistor connected between a first and second potential sources, and a first output terminal configured to changeably connect to a connection position in the first resistor so as to vary an obtained output voltage. The rear side voltage divider includes a second resistor connected between the first output terminal and a third potential source; and a second output terminal configured to changeably connect to a connection position in the second resistor so as to vary an obtained output voltage. The oscillation unit includes a variable capacitance element with a capacitance varied according to the output voltage from the second output terminal. The oscillation unit varies an output frequency based on a variation in a resonance point associated with a variation in the capacitance.