A method and apparatus for providing a suitable soft keyboard for end users to conveniently enter data to a portable information terminal that can not provide concurrently multiple character set keyboards, such as Korean, English, and Numeric keyboards. A data input assisting method displays an input window including a plurality of input fields when data input is requested. The input window identifies an input data set among English, Numeric, and non-English character sets suitable to an input field, which is selected for information input on the displayed input window, and provides a soft keyboard of touch screen or the like including the identified character set. Therefore, data input is ensured when a user must select and enter non-English (e.g., Korean), English, or Numeric data to match information type of each data field to be stored in a portable information terminal, such as a Personal Digital Assistant (PDA).