The purpose of this study is focused on revealing teenager characteristics and mass culture in the end of the 20th century, and researching the general traits of teenager costume in the latter half of the `90s and the typical style based on the analysis of the teenager culture. The result of this study are following as; The general traits of teenager costume are classified with sports-orientation, brand-orientation, and foreign street fashion-orientation. Typical styles are classified with sportive look, hiphop look, and funny look. Sportive look became the core of the street fashion developed with the street sports in the city, and presented the practical use with the fashionability mixing sportswear such as hightech snickers, sports character wear and items. Hiphop look, the genderless fashion, expresses teenager`s free life style and the diversiied sensibility and deconstructs the border of gender, racism. Funny look accepts the burden of the millenium as a humor and presents katharsis by creating unexpected style. The contemporary costume of teenager deconstructs the fixed idea about mix and match, good taste and bad taste, gender, coordination suited with T.P.O and intends ‘open costume’ for 21st century.