A communication apparatus comprising: an antenna configured to transmit and receive a signal through near field communication; a signal processing circuit configured to process the signal transmitted and received by the antenna; and a capacitive element arranged in series between the antenna and the signal processing circuit; characterized by an external power supply terminal configured to receive supply of a voltage from an external power supply; a voltage monitor unit configured to monitor whether a voltage to cause the communication apparatus to operate is supplied from the external power supply via the external power supply terminal or from another communication apparatus via the antenna and output operation mode information representing whether a voltage is applied from the external power supply; a storing unit configured to store a reference table that associates a capacity value of the capacitive element with whether a voltage is applied from the external power supply and with a plurality of communication standards; and a control unit configured to control the capacity value of the capacitive element, wherein the antenna receives a signal transmitted from the another communication apparatus and including communication standard information for specifying a communication standard, the control unit reads out, from the reference table, a capacity value corresponding to the communication standard information included in the received signal and the operation mode information output by the voltage monitor unit and changes a present capacity value of the capacitive element to the read-out capacity value, the capacity value read out from the reference table is a value different according to the communication standard information and the operation mode information, the control unit sets the capacity value such that a resonance characteristic is a maximum at a frequency of a carrier wave when the voltage is not applied from the external power supply, and sets the capacity value such that the resonance characteristic is the maximum at a frequency of a modulation signal near the carrier wave when the voltage is applied from the external power supply an antenna configured to transmit and receive a signal through near field communication; a signal processing circuit configured to process the signal transmitted and received by the antenna; and a capacitive element arranged in series between the antenna and the signal processing circuit; characterized by an external power supply terminal configured to receive supply of a voltage from an external power supply; a voltage monitor unit configured to monitor whether a voltage to cause the communication apparatus to operate is supplied from the external power supply via the external power supply terminal or from another communication apparatus via the antenna and output operation mode information representing whether a voltage is applied from the external power supply; a storing unit configured to store a reference table that associates a capacity value of the capacitive element with whether a voltage is applied from the external power supply and with a plurality of communication standards; and a control unit configured to control the capacity value of the capacitive element, wherein the antenna receives a signal transmitted from the another communication apparatus and including communication standard information for specifying a communication standard, the control unit reads out, from the reference table, a capacity value corresponding to the communication standard information included in the received signal and the operation mode information output by the voltage monitor unit and changes a present capacity value of the capacitive element to the read-out capacity value, the capacity value read out from the reference table is a value different according to the communication standard information and the operation mode information, the control unit sets the capacity value such that a resonance characteristic is a maximum at a frequency of a carrier wave when the voltage is not applied from the external power supply, and sets the capacity value such that the resonance characteristic is the maximum at a frequency of a modulation signal near the carrier wave when the voltage is applied from the external power supply