To efficiently display text data on a display screen easily to watch by transforming these text data to a display format appropriate for the size of an allocated display area.

On a data display device 1, the size and form of the display area in a display picture 5 are managed by a managing means 8 and in the case of a multiwindow system, for example, the size of each window to be opened on the screen is managed. Based on class information, a discriminating means 7 discriminates the class of display object data and when it is discriminated as text data, a changing means 9 transforms these text data to the display format ignoring a line partition code. Then, a display means 6 displays out these text data in the allocated display area. The text data become the line partition canceled character information strings and according to the lateral width setting value of the display area, these character information strings are returned and displayed. Then, the text data are displayed out while being formatted appropriately for the size of the allocated display area.