The middle aged women are. in general experiencing sudden psychological ageing by having grandchildren. The theoretical concept analysis on the process of becoming a grandmother from middle aged women are not well established. This study aimed at elucidating the conceptual meaning of becoming a grandmother by using Walker & Avant method. Interviews were made with 5 middle aged women who had grandchildren. The subjects were requested to express their feelings on becoming a grandmother. The attributive concept of becoming a grandmother included (1) attachment, (2) relationship, (3) changeability, (4) support, and (5) differentiation. The definition of a grandmother in Korean dictionary is father's mother or friendly term for elderly women. The definition of becoming is to turn into a certain position or status, to reach a certain age, relation. However, "becoming a grandmother" does not mean elderliness and ageing, but it means changing the roles in the family from a mother to a grandmother. In order to facilitate the role change smoothly, a teaching program is needed for grandmothers to adopt a new role in the family.