on the above described thumbnail image data note that at step s 603 determination about whether or not there is a difference in the color difference component may be made in consideration of all pixels of each image data alternatively the determination may be made in consideration of a portion of pixels e g pixels near the center of the image of each image data if determination is made in consideration of a portion of the pixels it is possible to reduce the processing load at step s 603 also in the present embodiment an image of a first frame is used as first image data however the present invention is not limited thereto for example a thumbnail image of a frame immediately before the second image data may be sequentially used as first image data for comparing a color difference component between the frame and a next frame as such in the present embodiment first image data whose color difference component is different from image data of a head of the moving image is retrieved and a thumbnail image corresponding to the image data is displayed as a digest whereby it is possible to prevent a black or white image from being displayed as a digest as a result it is possible to display a significant digest screen allowing the user to easily grasp the contents of the moving image stored in the optical disk 1 note that compared to the fourth embodiment the above mentioned third embodiment has the following advantages comparison of a color difference of each pixel requires a smaller processing load since the significance of an image is determined based on a thumbnail image whose size is smaller than an original.