A method used in an access module that uses a file system to manage a nonvolatile memory of an information recording module enables an available storage space to be calculated in a short time before file data is recorded, and shortens the time required from initialization of the file system to recording. An access module (1) manages information about area management of the file system configured in an information recording module in units of fixed-length blocks. A divisional available storage space calculation unit (103) performs an available storage space calculation process in units of the fixed-length blocks, and completes preparations for recording when detecting a minimum required storage space for recording file data and enables recording of the file data. This shortens the time required from initialization of the file system to recording.