A digest image preparation apparatus includes an image coding circuit for receiving a moving picture to output a coded image obtained by coding the moving picture and extracting a certaing feature parameters produced upon the coding to be outputted, a feature vector computation circuit for receiving the feature parameters to output feature vectors of image frames defined in n dimensions and a curve simplification circuit for simplifying loci generated by arranging the n-dimensional feature vectors outputted by the feature vector computation circuit in time series manner to output ranking information. It then becomes possible to reduce a necessary cost for the image coding and a ranking information calculation.