A method and an apparatus for diagnosing memory leak. The method includes: tracing the allocation of objects; recording allocation paths and allocation time of each object; giving to each object one unique identifier (ID) corresponding to an allocation path; determining the allocation path to which each object belongs; organizing the objects which are allocated but still not collected, and counting the age generations of the objects of the similar type according to the allocation time of each object; ranking the allocation paths according to the age generations of the surviving objects; and analyzing the ranking of the allocation paths, in which the allocation path with higher rank is more probable to introduce memory leaks. Thus, the suspicious allocation path possibly incurring memory leaks is selected and reported to the user for analysis.