The purpose of this study is to understand the concept of a sexual image and verify the method of its design expression through case studies of the sexual image evening dress shown in an Haute Couture Collection over the last 10 years (2005~2014). The results of analysis are as follows: First, “expression by the seeing through of the natural body” expressed a natural sexual image that combined fashion of the previous times with the beauty of the natural body by using a see-through material and classic or ethnic image. Second, “expression of a sexual-image look that emphasizes romantic detail” illustrated a romantic sexual image that emphasizes feminine sensitivity by mixing various ornamental elements such as see-through material and symbolism of underwear image. Third, “creation of a nude look using skin color” expressed sexual image of an evening dress by inducing erotic sexual association through a combination of opaque material of skin color and design shape that is intended for body exposure. Fourth, “combination of sexual symbol and heterogeneous elements” expressed a decadent, avant-garde and futuristic sexual images by using women’s underwear and a sexual symbol as design motif and mixed with mismatching elements. Fifth, “use of a fantastic black image” expressed an exclusive and refined sexual image and a decadent and primitive sexual image by using a fantastic image of black color. The results of this study are expected to be used for the design process of the eveningdress industry that aims for quality improvement.