This study investigates the costumes of the Most Reverend Priest, which shows a portrait of the Buddhist monk in Koryo dynasty, owned by SONG KWANG Temple. A surplice(袈裟) and a long sleeved Buddhist robe(長衫) was chiefly shown up a portrait of a Buddhist monk. The purpose of this study find out the color, form, pattern, material, adornment of the costumes which is appeared a portrait, and also seek to changing process according to the times. the finding in this paper are * A surplice - color : red, green, yellow etc. form : big size surplice, provision surplice. pattern : no. material : unstriated silk. adornment : bolt, ribbon. * A long sleeved Buddhist robe - color : grey, blue, dark blue, pink, green, chestnut,etc. pattern : no. In comparison with a survery of previous studies of Buddhist comstumes, the color and type of the Koryo dynasty are more brilliant various color. In other words, the social status of monk in the Koryo is higher than present day.