An information storage apparatus capable of setting the number and sizes of partitioned areas resulting from partitioning a memory area based on a user's intention is provided. For this purpose, an information storage apparatus having a plurality of partitioned areas of different security levels in a memory area is provided with an area control section that controls addresses of partitioned areas in the memory area, an area update condition control section that controls update conditions when the number or sizes of partitioned areas are updated, an area update decision section that decides whether a partition request requesting updating of the number or sizes of partitioned areas satisfies the update conditions and an area update section that executes, when the partition request satisfies the update conditions, updating of the partitioned areas in the memory area according to the partition request. The partitioned areas in the memory area of this information storage apparatus are updated at a partition request reflecting the user's intention in accordance with the user's intention.