To automatically find an object having a reference relationship which is not considered as a normal one by a user, by using an indicated condition and to show a reason why collection is not carried out by a garbage collection function for shortening time for memory leak cause investigation.

In a memory area accessible by an active program, data generated in a certain area are inspected to determine whether data corresponding to a set abnormal condition are included.When such data are included, reference relationships to the data are classified into allowed reference relations and prohibited reference relations. An abnormal condition of data in the memory and a classification rule for reference relationships to certain data are previously set before running the program or may be set while running the program. Finally, prohibited reference relationship information is outputted as an alert. The classified reference relationship is displayed in the form of a graph showing the reference relationship between the data according to its permission/prohibition for direct appeal to vision of the user.