The purpose of this study is to examine actual design cases of decorative detail in the Art Nouveau style from the end of 19th century to the beginning of 20th century, and create designs and fashion works to meet our contemporary fashion trends by means of over-decorative style, a characteristic of decorative detail. The characteristics of decorative detail in the Art Nouveau style can be outlined as follows: First, pleats appear with two major feels of solidity, undulated and curvilinear solidity based on gather(ruffle, frill/ flare and flounce) and regular and linear solidity based on linear pleats or tucks. Second, embroidery appears in various patterns developed with stitch of solid feel as well as a variety of coloration effects. Third, attachments are expressed by means of independent motif(applique, gloss effects(beads, sequins), affluent texture and mobility(fur, feather). Moreover, according to technical characteristics and expressive aspects of pleats, embroidery and attachments, it is found that decoration detail in the era of Art Nouveau is over-decoration style. Indeed, it appears in major expressive aspects such as rhythmical solid type, detailed prominence type, superficial touch type and profound volume type.