A communication apparatus comprising: a communication circuit unit configured to process a radio-frequency signal for transmitting data; an electric-field-coupling antenna configured to establish electric-field coupling to a communication partner facing the communication apparatus at a very short distance, wherein the electric-field-coupling antenna includes: a coupling electrode; and a resonating section, wherein the resonating section includes a distributed-constant circuit configured to strengthen electrical coupling between the coupling electrode of the communication apparatus and a coupling electrode of the communication partner, and wherein the radio-frequency signal is transmitted as an electric-field longitudinal wave component of electric-field-coupling between the electric-field-coupling antenna of the communication apparatus and an electric-field-coupling antenna of the communication partner, and the electric-field-coupling antenna is mounted on a printed circuit board on which a circuit module constituting the communication circuit unit configured to process the radio-frequency signal for transmitting data is provided, the communication apparatus being characterised in that: the distributed-constant circuit is configured as a stub including a conductive pattern disposed on the printed circuit board; and wherein ground is formed on another surface of the printed circuit board, a tip portion of the stub being connected to the ground via a through hole provided in the printed circuit board; and wherein the radio-frequency signal is an ultra-wideband signal using an ultra-wideband of radio frequencies. a communication circuit unit configured to process a radio-frequency signal for transmitting data; an electric-field-coupling antenna configured to establish electric-field coupling to a communication partner facing the communication apparatus at a very short distance, wherein the electric-field-coupling antenna includes: a coupling electrode; and a resonating section, wherein the resonating section includes a distributed-constant circuit configured to strengthen electrical coupling between the coupling electrode of the communication apparatus and a coupling electrode of the communication partner, and wherein the radio-frequency signal is transmitted as an electric-field longitudinal wave component of electric-field-coupling between the electric-field-coupling antenna of the communication apparatus and an electric-field-coupling antenna of the communication partner, and the electric-field-coupling antenna is mounted on a printed circuit board on which a circuit module constituting the communication circuit unit configured to process the radio-frequency signal for transmitting data is provided, the communication apparatus being characterised in that: the distributed-constant circuit is configured as a stub including a conductive pattern disposed on the printed circuit board; and wherein ground is formed on another surface of the printed circuit board, a tip portion of the stub being connected to the ground via a through hole provided in the printed circuit board; and wherein the radio-frequency signal is an ultra-wideband signal using an ultra-wideband of radio frequencies. the distributed-constant circuit is configured as a stub including a conductive pattern disposed on the printed circuit board; and wherein ground is formed on another surface of the printed circuit board, a tip portion of the stub being connected to the ground via a through hole provided in the printed circuit board; and wherein the radio-frequency signal is an ultra-wideband signal using an ultra-wideband of radio frequencies.