To easily edit a document file.

A server 4 converts file data of the document file to document image data 33, and generates a search file in which the document image data 33 is associated with the file data of the original document file. Based on the document image data 33 displayed on a LCD 14 of a mobile phone 3, edition data 57 obtained by selecting the start point and the end point of a range to be deleted is transmitted to the server 4. The server 4 reads out file data in the search file generated at the point of receiving the edition data 57, and deletes the range surrounded by the file start-point and end-point coordinates converted based on the edition data 57. The edited file data is converted to edited document image data 59 and transmitted to the mobile phone 3. When a determination button 55 is selected in a state where the edited document image data 59 is displayed on the LCD 14, a CPU 22 of the server 4 reflects the edited file data on the original document file and overwrites the original document file.