A method for transmitting a character message in a mobile communication terminal during a conversation by telephone comprises the steps of setting the mobile communication terminal to a character message-transmitting/receiving mode. The character message-transmitting/receiving mode is set while in a state in which a speech path has been established between the mobile communication terminal and a mobile communication terminal of a party other than the user. A character message is input at the mobile communication terminal by the user while in the character message-transmitting/receiving mode. Also while in the character message-transmitting/receiving mode, the mobile communication terminal processes the written character message and transmits the written character message to the mobile communication terminal of the other party via the established speech path.