A memory management method is provided to manage a memory in which areas of a garbage collected Java heap memory and a non-garbage collected external heap memory can be secured, by using a program executed by a processor in a computer. If it is judged that there is no reference to all data arranged in the external heap memory or starting point data of reference relations included in the all data, from data arranged outside the external heap memory, then the external heap memory is judged to be capable of being deallocated. As a result, it becomes possible to implement memory management in which garbage collection needing a long time program stop is not conducted and an additional API is not used.