A control device according to the present invention is provided with (A) a variable capacitance device including a variable capacitance element, and (B) a control unit configured to apply a control voltage with a first polarity to the variable capacitance device during a third period including a first period to perform communication using the variable capacitance device and a second period not to perform communication before the first period, and configured to apply a control voltage with a second polarity opposite to the first polarity to the variable capacitance device during a sixth period including a fourth period to perform communication and a fifth period not to perform communication before the fourth period.