A method for writing data includes: data maintaining step for maintaining writing object data to each of a plurality of memory devices; obtaining step for obtaining identification information assigned to each of the plurality of memory devices; generating step for generating combination data by associating and combining the identification information and the writing object data with respect to the plurality of memory devices; and sending step for sending the combination data to the plurality of memory devices; which are performed by a writing device. The method also includes receiving step for receiving the combination data; extracting step for extracting the writing object data corresponding to the memory device on the basis of the identification information from the combination data; and memorizing step for memorizing the target data for writing extracted from the combination data; which are performed by each of the plurality of memory devices.