An image processing apparatus includes: a user input interface configured to provide a user input according to at least one input method; a storage configured to store a database for biometric information of at least one user which corresponds with at least one identification (IDs) previously registered to the image processing apparatus; a signal processor configured to process a preset service which is provided corresponding to an authenticated identification (ID) in response to a user being authenticated with the ID; and a controller configured to determine whether authentication is performed with regard to one of the IDs in response to an event occurring which identifies a current user, and retrieve and authenticate the ID from the database based on the biometric information of the current user acquired by the user input interface in response to determining that the authentication is not performed with regard to the ID.
