In this paper, the concept of life-style will be redefined and reformulated through examining Max Weber's "Lebensfuhrung". This article is composed of two parts. In the first, it is clarified that his "Lebensfuhrung" has two aspects: maintaining the social structure (Japanese version of it, "seikatsu-yoshiki") and changing it (Japanese version of it, "seikatsu-taido"), and that they are mutually related. Secondly it is traced how the theory of lif-style has been developped, and the life-style is redefined from the viewpoint of life-system. The life-style is a patterned ethos, motivated by his own "life-needs" and directed by his own "life-value", according to which an actor or agent should choose "life-relationship" and "life-resources". As his life-style is collectively shared, it becomes a factor of social change. When the life-styles in the "life-world" are incorporated into the present social system, then a social transformation process initiated by the actor or agent of life-style will be terminated.