This study suggests designs of maternity clothes wearable after childbirth and aims at confirming that maternity wear is continuously wearable during a post-natal period. As for research methods, theoretical and empirical studies with research on a production of work were conducted, focusing on the design development of the maternity dress which may be worn even after childbirth. The results of theoretical and empirical studies possibly presented various designs which require fashionability going with the trend of time. The maternity wear also requires the adaptability for a changing body shape to enable a woman to wear it during a pregnancy period and after childbirth. Besides, the convenience of dressing and undressing with wearing comfort is considered. 6 sets of one-piece dress were made as the result of the study and three factors of fashionability, adaptability and convenience were considered. The conclusions are as follows : Firstly, it verified that the maternity wear is fashionable clothes not to cover protruded abdomen but to satisfy women's desire of self expression. Secondly, it overcame the limit of dress design through fitting it to completely different two body sizes and shapes with design factors and patterns. Lastly, it suggested a research model of maternity wear corresponding to economical, environmental and ethical principles as giving an effect of “two” dresses with one. This study presented a new direction of design study with meaningful actions of fashion designing in the aspects of economical, environmental and ethical consumption unlike artificial disposal on SPA brands.