A voltage smoothing circuit includes a multilayer capacitor including a first capacitance unit and a second capacitance unit and a regulator including an input terminal which is electrically connected to the second capacitance unit and an output terminal which is electrically connected to the first capacitance unit. The regulator calculates a first voltage which is applied to the first capacitance unit based on a second voltage which is applied to the second capacitance unit from the input terminal such that a potential difference which is applied to the first capacitance unit decreases or increases when a potential difference which is applied to the second capacitance unit increases or decreases, and outputs the first voltage from the output terminal.