A logging unit logs data, including data on object generation/access and start/end of GC, information about object longevity when GC is performed, and data about a method call/return or the like. An analyzing unit organizes by object logged records, sorts that information about each object by time or size, and obtains changes in required heap size and a longevity characteristic of each object. An estimating unit uses a required heap size data and the object longevity characteristic to estimate an optimum heap size according to a criterion specified by a user.