Disclosed herein are a method and apparatus for providing a combined authentication service. Combined authentication information is set by acquiring an entry window location and authentication characters from a user, an entry window including the entry keypad is displayed at the entry window location, entry information including entry characters and entry coordinates is acquired from the user via the entry window, and combined authentication is performed by verifying the entry characters and the entry coordinates, thus strengthening the security of authentication of a mobile terminal while maintaining the user's existing password. Further, if a region to which the password entry coordinates are to be mapped is selected when the user sets a password, authentication is performed by additionally considering mapping coordinates in addition to the password even if the user enters the password into the existing password entry window, thus strengthening the security of password authentication.