The file recording method of the present invention is a method for recording a file on an information medium including at least both a specific area and a data area. In the method, a reserved area is allocated previously as a part of a recording file, from a current recording location of the recording file under recording on the data area, and at the same time, management information of the recording file including the reserved area is recorded on the specific area. When recording data additionally on the recording file, the data are recorded on the reserved area from the recording location. Thereby, the concentration of rewriting of the management information of a file system to a storage area is avoided while compatibility with an existing file system is maintained, and thus the life of the information medium is extended.