1. A character input device that carries out an input and an edit of characters, said character input device comprising: a key input unit for accepting a command to input and edit said characters; a character string edit control unit for controlling an edit and confirmation of a character string in response to the command from said key input unit; a character string prediction engine unit for receiving a character string as an input and predicting a character string including said character string and subsequent characters; a character string input processing unit for acquiring candidates for the character string predicted by said character string prediction engine unit; a confirmed character string information storing unit for storing information on a character string selected from said candidates acquired as information on a confirmed character string in a confirmed state; a character string confirmed state determining unit for determining whether or the character string edited by said character string edit control unit is in said confirmed state; and an input character string display unit for displaying the character string edited by said character string edit control unit, wherein said key input unit has a single correction key, and, when said correction key is operated while said character string is not in the confirmed state, outputs a command to delete said inputted character string to said character string edit control unit, and, when said correction key is operated while said character string is in the confirmed state, outputs a command to change said confirmed character string to an unconfirmed state to said character string edit control unit.