1. An apparatus for generating icons for moving images, comprising: a decision device that decides a shape and a color of each of a plurality of moving-image icons of a plurality of moving-image files based upon the plurality of moving-image files and a maximum size and a minimum size among sizes of images of frames constituting moving images representing moving-image data that has been stored in said plurality of moving-image files; and a generating device that generates data representing a moving-image icon having the shape and color decided by said decision device, wherein said decision device decides the shape and the color of the plurality of moving-image icons based upon said moving-image data stored in said plurality of moving-image files identified by said moving-image icons and moving-image data stored in other moving-image fires, wherein said moving-image icons comprise a rectangular cube shape and said decision device decides a dimension of at least one side of the rectangular cube shape based upon a playback time, wherein said color comprises a degree of lightness, the degree of lightness of said each of a plurality of moving-image icons being decided by the size of the moving image file, and wherein said decision device decides a horizontal size LI based upon LI=I+(Hx−Hmin)/L0, wherein L0 is an incremental value equal to (Hmax−Hmin)/(S−1), where Hmax represents a maximum value of a number of pixels in the horizontal direction of all image sizes of all moving-image files, Hmin represents a minimum value of a number of pixels in the horizontal direction of all image sizes of all moving-image files, S represents a number of steps it takes to make a change from the minimum value to the maximum value, and Hx represents a number of pixels in the horizontal direction of image size of a moving image identified by a moving-image icon for which size LI is to be calculated.