11. A portable device comprising: a communication unit configured to communicate at least one dialog for a group chat with a server; a display unit; an input unit; and a controller configured to: control the display unit to display a group chatting window for the group chat, if a request of a user of the portable device for the group chat is detected, detect a request for an extraction of a dialog for at least one certain conversation partner of conversation partners in the group chat, extract the dialog of the at least one certain conversation partner from one or more dialogs if the request for the extraction of the dialog is detected through the input unit, and control the display unit to display the extracted dialog on a sub-chatting window, wherein the controller extracts automatically the dialog of the at least one certain conversation partner during the group chatting, and controls the display unit to display the dialog on the sub-chatting window.
11. A portable device comprising: a communication unit configured to communicate at least one dialog for a group chat with a server; a display unit; an input unit; and a controller configured to: control the display unit to display a group chatting window for the group chat, if a request of a user of the portable device for the group chat is detected, detect a request for an extraction of a dialog for at least one certain conversation partner of conversation partners in the group chat, extract the dialog of the at least one certain conversation partner from one or more dialogs if the request for the extraction of the dialog is detected through the input unit, and control the display unit to display the extracted dialog on a sub-chatting window, wherein the controller extracts automatically the dialog of the at least one certain conversation partner during the group chatting, and controls the display unit to display the dialog on the sub-chatting window. 18. The portable device of claim 11 , wherein the controller receives an input of adding a certain conversation partner through the input unit if a request for an addition of the certain conversation partner is detected through the input unit, extracts a dialog of the certain conversation partner to be added, and controls the display unit to display the extracted dialog of the certain conversation partner to be added on the sub-chatting window.