1. A hologram-reproducing method adapted to obtain a reproduced image by irradiating a hologram-recording material with a reference-light beam so that a reproduction signal-light beam is generated and picking up an image of the reproduction signal-light beam, the hologram-reproducing method comprising the steps of: generating a plurality of reproduced images by irradiating the hologram-recording material with a plurality of reference-light beams including the step of obtaining a predetermined area of an image, the predetermined area being used for performing image processing adapted to generate a sequence of consecutive reproduced images by picking up the image of the reproduction signal-light beam consecutively on the basis of a time-varying total of brightness values corresponding to at least one region of the image; and generating a single reproduced image by performing image processing for the plurality of reproduced images.