An apparatus for automatically switching language input modes including a first unit, to determine whether to turn on an automatic language input mode switching function; a second unit to bypass a current keystroke input via a predetermined input device when the control signal is an off signal, the second unit either bypasses the current keystroke or deletes previous keystrokes and converts the previous keystroke(s) and the current keystroke into their respective language counterparts according to recognizing a language input mode of a scan code of the current keystroke when the control signal is an on signal; and a third unit to recognize the language input mode of the scan code of the current keystroke by referring to language dictionaries and provide a current language input mode, the recognized language input mode of the current keystroke, keystroke deletion range information, and keystroke conversion range information to the second unit.