An object is to prevent lowering of a dynamic range of a hologram recording medium without lowering an average data transfer rate, and to provide stabilized recording sensitivity. A scheduler determines a recording interval time from the point of time when light is irradiated to record a certain hologram of holograms to be multiplex-recorded to the point of time when light is irradiated to record a succeeding hologram in such a manner that at least parts of the holograms are recorded one over the other in a certain recording area. A recording interval time controller controls a light source to irradiate the light depending on the recording interval time determined by the scheduler.