a first communication unit;

a database configured to store device information of an external electronic device for which communication with the first communication unit has been connected;

a memory configured to store at least one instruction; and

a processor configured to execute the at least one instruction,

wherein the processor is configured to:

determine whether the external electronic device has been changed at a second time point on the basis of device information stored in the database at a first time point and device information of the external electronic device at the second time point, and

perform an operation of resetting a remote controller that remotely controls both the display device and the external electronic device if the external electronic device has been changed at the second time point,

wherein if a NULL information, which indicates that identification information of the external electronic device connected to the display device is unknown, is received at the second time point, identification information selected by a user is determined as device information,

wherein the device information is any one of the NULL information and identification information of the external electronic device,

wherein:

the external electronic device does not transmit device information at the second time point, and the device information of the external electronic device at the second time point is the NULL information, and

the processor determines that the external electronic device has been changed when the device information stored at the first time point is first identification information, and

further comprising a display,

wherein the database matches and stores identification information of at least one first external electronic device for which communication with the first communication unit had been connected and remote controller setting information of the at least one first external electronic device,

if the external electronic device does not transmit device information at the second time point and it is determined that the external electronic device has been changed, the display displays the identification information of the at least one first external electronic device, and

when identification information of any one first external electronic device among the displayed identification information of the first external electronic devices is selected by a user, the processor performs an operation of resetting the remote controller by using remote controller setting information matched with the identification information of the any one first external electronic device.