The present invention discloses a writable storage medium with backup module contained therein to backup important data. With this writable storage medium, the user could automatically duplicate the data in the computer or the peripheral devices coupled thereto into the writable storage medium. All the user has to do is designating the target data to be duplicated, and the backup module will finish the rest. No installation of software is required. The user may recover any part of the target from the writable storage medium if the computer is crash or some important files are deleted accidentally. Hence, a simple and direct way for data backup is provided by the present invention.