An apparatus for preventing loss of an item and quickly searching for the item includes a slave configured to act as a radio frequency identification (RFID) tag having unique identifier information in an internal tag memory; and a hand-held master configured to function as an RFID reader and to permit the change of at least one of a recognition distance and a recognition width, at which the master recognizes the slave. When the distance between a user and an item is out of a predetermined range, a warning such as an alarm or voice signal is provided to the user, so that it is possible to prevent loss of the item. Alternatively, it is possible to quickly search for a misplaced item whenever the user desires it and has misplaced the same.