A memory management method, which is used in a computer including a CPU and a memory to unload an area no longer necessary out of a memory area used by a program stored in the memory and executed by the CPU, comprising: generating a first processing system for executing the program in the memory; generating a second processing system in the memory when a first opportunity occurs; copying a content of a memory area of the first processing system to a memory area of the second processing system; determining an unnecessary area out of the copied memory area of the second processing system; transmitting a determination result regarding the unnecessary area to the program of the first processing system when a second opportunity occurs receiving the determination result; unloading the unnecessary area in the memory area of the first processing system.