An oscillation circuit is connected to a resonator element (crystal resonator) and oscillates a resonator element to output an oscillation signal. The oscillation circuit includes an amplification element (inverter), and a set of variable capacitive elements having at least two variable capacitive elements, which are connected to an oscillation loop from an output to an input of the amplification element and the capacitance values thereof are controlled with potential differences between reference voltages and a variable control voltage. In each variable capacitive element of a set of variable capacitive elements, the common control voltage is applied to one terminal, and the reference voltage which differs between the variable capacitive elements is input to the other terminal.