At least two devices having different characteristics are provided as one file system, and the file system stores a file in a device according to the file purpose. In file system operation, a device characteristic acquiring unit acquires characteristic information of the respective devices by using a device characteristic database, a device characteristic acquiring interface, and stores the information in the device characteristic holding. In file operation for preparing file management information in file storing process, a file purpose interpreting unit interprets the purpose and attribute of the file and registers a characteristic flag representing the characteristic of the file in the file management information. In file operation for actually writing a file, a storage device decision unit decides a file storage location device on the characteristic flag in the file management information and information of the device characteristic holding unit to perform a device free region securing process.