Disclosed is a apparatus and a method for displaying various character effects on a character input screen of a mobile station using a differentiated graphic element according to a key input signal. In the method a visual character theme set by a user is displayed in a character input mode, and a character input effect corresponding to the visual character theme is shown according to a key input signal. Accordingly, since the mobile station can show a visual character input effect in every key input sequence by allowing the user to select a desired visual character theme in advance, an entertaining effect is added to a user interface of the mobile station.