A sequence of operators produced for some situation by a planning system cannot be applied under the different situation. In such case, a new plan have to be constructed to satisfy the new situation. However it is inefficient to reconsult the whole plan when the plan can be modified in order to be applied for the current situation. The system proposed in this paper can modify the plan to adapt to the new situation with the least change from the old plan. The system consists of three parts ; planner, effect-investigating system and Problem Create System. The planning system behaves like the NOAH [Sacerdoti 75] to produce operators as the network which can achieve goal states from initial states. The effect-investigating system detects harmful effects caused by changed situation by way of TMS [Doyle 79] from the network which consists of facts (operators and conditions) produced by planner with justification which represents dependency of these facts. The PRCS establishes problem (goal states) which should be solved by planner to modify the invalid plan for current states.