1. A moving picture converting apparatus for restoring a string of thinned images resulted from thinning pixels of an original-image string, the apparatus comprising: an input unit to receive the thinned-image string; an initial motion vector detector to detect a string of motion vector images on the basis of the thinned-image string; a reconstructing unit to reconstruct, each time a new motion vector image string is detected, a string of restored images on the basis of the new restored-image string and previous detected-motion vector image strings; a motion vector detector to detect, each time a new string of restored images is reconstructed, a new string of motion vector images based on the new restored-image string and previous detected-motion vector image string; and a process terminating unit to terminate the reconstructing process by the reconstructing unit and motion vector detecting process by the motion vector detector and output a restored image, which has been to be restored, of the restored-image string obtained at the time of deciding the process termination.