Requirements changes frequently occur at any time of a software development process and their management is a crucial issue to develop software of high quality. Meanwhile, recently goal-oriented analysis techniques are being put into practice to elicit requirements. In this situation, the change management of goal graphs and its support is necessary. This paper presents two topics related to change management of goal graphs; 1) version control of goal graphs and 2) impact analysis on a goal graph when its modifications occur. In our version control system, we extract the differences between successive versions of a goal graph by means of monitoring modification operations performed through a goal graph editor, and store them in a repository. Our impact analysis detects conflicts that arise when a new goal is added, and investigates the achievability of the other goals when the existing goal is deleted.