Our society is becoming an aged society. There are increasing human beings who have incomplete mental ability in our society. Under the current civil law, incompetence and quasi-incompetence system are used in case of deterioration of mental judgement. But the system is rigid because it only provides two types by law despite of being various degrees of mental judgement. Once incompetence or quasi-incompetence is pronounced by a court, it is recorded in the registration of family relationship. In addition, there are social prejudice against the words such as incompetence and quasi-incompetence. Hence, there are hardly anyone who use this system, and the system is practically not being used and is ending up as a mere scrap paper. Therefore, in order to actively deal with these problems, we are trying to reform this system or to enforce the new adult guardianship laws. So, this study is designed to meet the needs of reforming the area of a guardianship for mentally incapacitated adults. When we reflect a new reform legislation, we should focus on respecting the human right and dignity of mentally incapacitated adults. And the new reform should guarantee their autonomy and minimize the public invention for assisting them. At the same time, their needs should be fully satisfied. In addition, it is desirable to introduce and enforce the new guardianship regime after fulfilling all the conditions necessary for the operation of the regime, such as proper organization, enough funds and relevant procedure. In particular, the guardianship in the aging society should focus on the protection of the aged more thorouly. To do this, it is indispensable to cultivate guardians for the adults more systematically.