The fundamental purpose of modern correctional treatment can be to surely make convicts return to society through individualization of treatment. However, it seems individualization of treatment may not be so helpful for convicts in returning to society unless it is the most appropriate and rational individual treatment that considers their property and character on the basis of exact understanding on each convict. Especially, as individual personality and property is emphasized and persons with different view of life, view of world and sense of value are living together nowadays, it seems almost impossible to return convicts to society merely through individualization of treatment, ignoring the fact that ‘proper sphere of character’ exists. Thus, seeking the method of correctional treatment appropriate to the age of individualization like the present time seems to be the most important task of modern correctional administration. The concept of individualization of treatment can be said to be established on the basis of ‘rational sense of human being’ that has ruled so far since the 17th century. Rational sense of human being may be image of human being that overlooks the fact that ‘proper sphere of character’ unique to each person obviously exists by grasping human being merely with abstract concept that human being is 'free and rational individual.' However, returning convicts to society through individualization of treatment based on rational sense of human being will be inevitably subject to regular limit. Therefore, it seems that so-called ‘personification of treatment’ is necessary which is based on the premise that each person has ‘proper sphere of character’ in the age of individualization like the present time. Needless to say, it may not be so easy to clearly define what ‘personification of treatment’ is and what it should be. Thus, it may be necessary to first find method to secure conversation and trust between characters or between individual character and community (society or correction authorities) before defining the concept of ‘personification of treatment.’ It is true that the correctional treatment has treated convicts not as ‘principal of correction’ or ‘partner of conversation’ but as ‘object of correction’ or ‘object of treatment’ thus far. I think that this is why so-called ‘personification of treatment’ is not realized which considers the property and character of convicts, based on the exact understanding on each of them. Therefore, in order to efficiently achieve the purpose of returning convicts to society in the present time, it is required to recognize convicts as ‘principal of correction’ or ‘partner of conversation’ and to enforce ‘personification of treatment’ on the basis of the fact that they also have ‘proper sphere of character.’