1. An information processor comprising: a central processing unit for controlling a frame extraction unit which extracts a plurality of frame sequences, each of the frame sequences being extracted from an identical moving image at different time intervals on a time axis of the moving image; a decoding unit which decodes data of the plurality of frame sequences extracted by the frame extraction unit; a display unit having a display screen which simultaneously displays a plurality of thumbnail arrays of decoded images, and an input unit which accepts a user's instruction for selecting a thumbnail array, from among a plurality of thumbnail arrays simultaneously displayed by the display unit, as a target to be shifted, forward or backward, wherein each thumbnail array corresponds to a particular one of the plurality of frame sequences, and each thumbnail in a thumbnail array represents one of the frame sequences in the corresponding particular one of the plurality of frame sequences, wherein the plurality of thumbnail arrays are displayed in the order of appearance in the moving image so that all of the displayed plurality of the thumbnail arrays include a thumbnail from each thumbnail array that represents a frame sequence that includes the same time on the time axis of the moving image, wherein the frame extraction unit identifies, in accordance with the user's instruction, a frame to be displayed in the selected thumbnail array after the shifting and further extracts frame data to be newly displayed; and wherein the display unit updates the selected thumbnail array with a frame identified by the frame extraction unit.