An image display device displaying an image signal input from an external device and transmitting a control signal corresponding to a user input signal for controlling the external device to a relay device , the image display device comprising: an external device interface unit configured to connect the image display device with the external device ; a display unit configured to display an image received from the external device ; a user input interface unit configured to receive an input signal and to send a control signal corresponding to the input signal to the relay device acting as a communication relay between the image display device and the external device ; and a controller configured to: in response to the image display device being powered on, check (S11, S12; S21, S22; S108) whether or not a connection log of the image display device includes a previous connection between the image display device and the relay device , scan (S14; S24) for an advertisement packet from the relay device at a first scan interval when the connection log does not include the previous connection between the image display device and the relay device , and scan (S13; S23; S109) for the advertisement packet from the relay device at a second scan interval having a longer time duration than the first scan interval when the connection log includes the previous connection between the image display device and the relay device . an external device interface unit configured to connect the image display device with the external device ; a display unit configured to display an image received from the external device ; a user input interface unit configured to receive an input signal and to send a control signal corresponding to the input signal to the relay device acting as a communication relay between the image display device and the external device ; and a controller configured to: in response to the image display device being powered on, check (S11, S12; S21, S22; S108) whether or not a connection log of the image display device includes a previous connection between the image display device and the relay device , scan (S14; S24) for an advertisement packet from the relay device at a first scan interval when the connection log does not include the previous connection between the image display device and the relay device , and scan (S13; S23; S109) for the advertisement packet from the relay device at a second scan interval having a longer time duration than the first scan interval when the connection log includes the previous connection between the image display device and the relay device . in response to the image display device being powered on, check (S11, S12; S21, S22; S108) whether or not a connection log of the image display device includes a previous connection between the image display device and the relay device , scan (S14; S24) for an advertisement packet from the relay device at a first scan interval when the connection log does not include the previous connection between the image display device and the relay device , and scan (S13; S23; S109) for the advertisement packet from the relay device at a second scan interval having a longer time duration than the first scan interval when the connection log includes the previous connection between the image display device and the relay device . <EOS>