A system for inputting information by utilizing an extension key. The system includes: an input unit having multiple division areas and detecting a division area selected by a user from among the multiple division areas; and an input analysis unit for allocating corresponding information to the multiple division areas and analyzing that if the input unit detects any of the multiple division areas being selected, information allocated to the selected division area is input, wherein multiple characters are allocated to each of the multiple division areas, when one or more of the division areas are selected, predicted words that are generated by combining characters allocated to the selected division area or areas according to an sequential order of the selected division area or areas are extracted and allocated to each of the division areas, and when a division area to which the predicted word is applied is selected by a predetermined method, the input analysis unit analyzes that the predicted word allocated to the division area which has been selected by the predetermined method is input.