An antenna device disclosed herein is integrated with an earphone for generating sound from an ear receiver, and connected to a wireless equipment through a connector to transmit an audio signal applied from the wireless equipment to the connector through a plurality of earphone signal lines. An antenna element lies between the ear receiver and an intermediate position of an earphone signal line for transmitting the audio signal from the connector to the ear receiver. A branch is disposed at the intermediate position for preventing a high frequency signal on each of the plurality of earphone signal lines from passing therethrough, and for passing the audio signal therethrough to extract a signal received by the antenna element. A coaxial line transmits the signal received by the antenna element and extracted by the branch to the connector through a core line possessed thereby.