An in-vehicle wireless communication device to be mounted on a vehicle and wirelessly communicating with a mobile terminal carried by a user of the vehicle, the in-vehicle wireless communication device comprising: a calibration information storage section adapted to store calibration information including a calibration coefficient for calibrating a radio wave intensity of the mobile terminal, a threshold intensity, obtained using a calibration coefficient, to be compared with the radio wave intensity, or a calibration coefficient for calculating the threshold intensity, the calibration information being for use in a state of identifying the mobile terminal; a wireless communication section adapted to perform wireless communication with the mobile terminal during mobile terminal registration and during a state of identifying the mobile terminal; a radio wave intensity detection section adapted to detect the radio wave intensity of a radio wave received from the mobile terminal during the wireless communication; a distance information detection section adapted to detect distance information to the mobile terminal based on a radio wave intensity of a radio wave received from the mobile terminal and the calibration information stored for the mobile terminal; a mobile terminal registration section adapted to register the mobile terminal as an authorized mobile terminal by wireless communication with the mobile terminal through the wireless communication section; and a calibration information registration section adapted to generate the calibration information for the authorized mobile terminal based on a radio wave intensity detected by the radio wave intensity detection section at the time of registration of the authorized mobile terminal, and to register the calibration information for the authorized mobile terminal in the calibration information storage section, characterized in that the mobile terminal registration section is adapted to request the mobile terminal to transmit a radio wave with a predetermined intensity at least at the time of registration. a calibration information storage section adapted to store calibration information including a calibration coefficient for calibrating a radio wave intensity of the mobile terminal, a threshold intensity, obtained using a calibration coefficient, to be compared with the radio wave intensity, or a calibration coefficient for calculating the threshold intensity, the calibration information being for use in a state of identifying the mobile terminal; a wireless communication section adapted to perform wireless communication with the mobile terminal during mobile terminal registration and during a state of identifying the mobile terminal; a radio wave intensity detection section adapted to detect the radio wave intensity of a radio wave received from the mobile terminal during the wireless communication; a distance information detection section adapted to detect distance information to the mobile terminal based on a radio wave intensity of a radio wave received from the mobile terminal and the calibration information stored for the mobile terminal; a mobile terminal registration section adapted to register the mobile terminal as an authorized mobile terminal by wireless communication with the mobile terminal through the wireless communication section; and a calibration information registration section adapted to generate the calibration information for the authorized mobile terminal based on a radio wave intensity detected by the radio wave intensity detection section at the time of registration of the authorized mobile terminal, and to register the calibration information for the authorized mobile terminal in the calibration information storage section, characterized in that the mobile terminal registration section is adapted to request the mobile terminal to transmit a radio wave with a predetermined intensity at least at the time of registration.