Provided is a data processing method that is capable of high-speed processing without using a large cache memory, while correlating 2-dimensional parameters with a plurality of data without damaging the arrangement rule. Therefore, when there is a continuing M-line parameter after a previously read M-line parameter in a 2-dimensional table that is stored in an external memory 406, the contents of the cache memory 404 are updated with this continuing M-line parameter as the new parameter. When there is no continuing M-line parameter after the previously read M-line parameter in the 2-dimensional table, the contents of the cache memory 404 are updated with the continuing M-line parameter after returning to the starting line of the 2-dimensional table as the new parameter. Such an update rule is maintained even when the band, which is the processing unit, is changed, or even in the progress of band processing.