The purpose of this study is to observe the symbolic meaning and the values of the costume which express bisexuality through the definition from a culture point of view. The research method is to contemplate the documentary records such as world history, art history and clothing history, and to recognize the symbolic meaning of a bisexuality in modern fashion design. A definition the word´man and woman´restricted the human being for a long time. This restrict is enforced by the costume, but this traditional fixed idea is retarded by the liberal sense of the human being and the design expresses a sex ambiguity This study inspects the sex ambiguity and the meaning of that through a cultural background and a historical costume. The results are as follows: The first, the cultural background about bisexuality is classified into the etymological point, the mythologic point. the art and philosophical point, the political and economic background, the mass media, and the custome and the regulation. A bisexuality is a concept in existence from ancient times. we have an open-minded attitude about bisexuality in the present than the past. The second, the function of costume is sex classification before 20th century, but since 20th century the costume expresses sex ambiguity. The third, the symbols of the bisexuality are the interminacy, the unity and the dismantling. The costume which expresses bisexuality means coexistence of male sex and female sex. this is a kind of motion to embody a ideal body of the human being. This study makes a contribution to recognize the dignity of human body and to understand the phenomenon of modern society.