To provide a method and device for displaying speech data graphically and more accurately by a computer system.

For a speech data file, frame size is selected first and the speech data file is divided into plural frames. At this time, the respective frames except the start frame include nearly the same number of speech data samples. Then plural variables are initialized. Then a starting data value, a maximum data value, a minimum data value, and a final data value are selected for each frame. Those four data values are stored in appropriate variables. Then the data selecting process is carried on until the final frame of the data file is reached. Lastly, the line obtained by connecting all selected data value points is displayed on a display device, frame by frame.