This study examined the characteristics of 45 sects of seven new aboriginal religious groups in Korea including Jeungsan sect, Tangun sect, Soowoon sect, Won Buddhism, Bongnam sect, Gahksedo sect, Shamanism sect that had given a considerable influence on the modem Korean society since the end of 19th century through the field study and the review of documents. The purpose of the study was to elucidate how their religious ideas were reflected in their ceremonial costumes and what characteristics these costumes had. The results were as follows: 1. The new religious groups in Korea modified or mixed the designs or the names of existing outfits to convey their ideas or beliefs through their costumes. 2. The costumes of new religious groups had common characteristics of the times, Korean tradition and ancestor worship. 3. All the ceremonial costumes symbolized the creeds and ideas of each religion in their names, designs, and colors. The names of the costumes such as Way-Robe, Law-Robe, and Ceremony-Robe, and of the headpieces such as Sky-Crown, Lotus-Crown, Ceremony-Crown, and Sevenfold-Crown, for instance, were related with Buddhism, Taoism, and Confucianism. The most common design of costume was consisted of traditional hanbok and some type of headpiece and robe for men, and hanbok modified to Western-style for women. Most sects adopted hanbok as their ceremonial costume, but they tend to simplify its design. The color scheme of the costumes reflected the influence of the Yul-Yang and Five Elements idea but the colors varied depending on seasons and occasions to suit their creeds and philosophy. 4. These religious costumes were worn at various ceremonies, ritual, and various anniversary services for the master and other dignitaries of the sect to render greater piety to those gatherings, to distinguish the sect from other religious groups, to clarify the meaning of the ceremony, and to heighten the devout feelings of the participants. Thus, the structure (the symbol, names, and types of the outfit, and their color scheme) and religious background of the costumes of the new aboriginal religious groups in Korea turned out to have inherited and mixed various elements of traditional Korean outfits and those of existing religions to symbolize their religious ideas.