Abstract: The present invention aims to provide a memory rewriting apparatus which can rewrite data stored in a memory of a portable terminal without stopping in the middle. According to the model of the portable terminal and the version number of data stored in each memory area of the memory, a memory area which requires rewriting is to be specified. An amount of remaining battery charge is compared to an estimated battery consumption for rewriting piece of data requiring the rewriting. In a case where the amount of remaining battery charge is sufficient, the memory rewriting apparatus transmits data to the portable terminal and specifies the memory area for the portable terminal.