The purpose of this thesis is to make clear particulartity of young adult generation which leads industry in their demands so that fashion trends are foresaw, and to describe style of costume satisfied with picture of new male. This thesis is to consider young adult style of costume in terms of double root described by W$ddot{o}$lfflin in the internal meaning and the external form, so as to analyze their unique style. In conclusion, domestic young adult style of costume is embodied in the internal meanings of individuality, aestheticism and new classicism in terms of the external forms which means body-priority-form by open-form, whole-form, integration-form, rounded-form, indeterminate-form. With these results, domestic fashion industry is demanded to be from classic to modern expressions so as to be reflected in sophisticated masculinity of young adult.