A method for effectively inputting characters in an ultra-compact mobile terminal is disclosed. When the mobile terminal enters a character input mode, one of a plurality of key groups having at least one key block is displayed by manipulation a scroll key in an up or down direction, and characters of the key blocks are displayed. Characters of the displayed key blocks and one character is selected using one of two selection keys or the scroll key operated in a push direction. Several characters are displayed in each of the key blocks and a character is selected by manipulating one of the two selection keys or pushing the scroll key a number of times. The selected character is displayed on a display unit.