The data processing method reversibly processing data information input to a data processing device by a processing unit including a data volume reducing unit reducing a data volume of the data information, and a developing unit reconstructing data information reduced in the data volume reducing unit. The processing unit is structured by overlaying processing layers formed of a plurality of cells. The data volume reducing unit performs unit processing on each of the plurality of cells having the data information. The unit processing performs identification processing by a weight according to equivalence and distance of data from a cell group adjacent to the cells, and reduces the cells by each of the processing layers in an order from a lower layer to an upper layer of the processing layers until a data position existing on a time axis of the cells stops to thereby reduces the data volume.