1. A motion picture playing method for playing a motion picture image on a display unit, comprising: obtaining a motion picture image; obtaining a character string to be scrolled and displayed in a predetermined direction being overlaid on the motion picture image obtained in the motion picture image-obtaining step; and controlling a display mode for scrolling and displaying the character string based on a length of the character string in the predetermined direction obtained in the character string-obtaining step and a playing time of the motion picture image obtained in the motion picture image-obtaining step.