PURPOSE: To effectively display an afterimage with less data capacity and simple processing concerning the game device for displaying the afterimage of a character to move.

CONSTITUTION: Data such as the moving direction, speed and position of the character are supplied to an afterimage display position deciding means 1 and corresponding to the moving direction and speed of the character, the display positions of the plural afterimages of the character are decided on the opposite side in the moving direction of the character. A transparency degree deciding means 2 decides the degrees of transparency for the respective after-images which display positions are decided. While using the shape data of the character, data showing the display positions of the respective afterimages and data showing the degrees of transparency for the respective afterimages, an afterimage data generating means 3 generates the image data of respective afterimages in the same shape as the character. While using the generated image data of respective afterimages, the image data of the character, the image data of a background picture on a screen and the image data of other objects on the screen, an image synthesizing means 4 synthesizes the image data of one picture so that the background pictures of respective afterimages can be made transparent corresponding to the degrees of transparency for respective afterimages.