For the purpose of application to new natural dyestuff, the dyeability of Rubus coreanus Miquel extract was analyzed. It was dyed in silk fabric according to various dye concentration, dyeing temperature, dyeing time, and dyeing repetition. And the effects of mordanting conditions were examined as color differences and color fastnesses. The maximum absorbance of Rubus coreanus Miquel extract was at 521 nm. The dyeaffinities were increased gradually as were increased dye concentration, dyeing temperature, dyeing time, and dyeing repetition. The dyeaffinity was increased at pre-mordanted condition, and color difference was increased distinctly at post mordanted condition. The hues of mordanted silk fabrics were RP, P, PB, BG where as non mordanted silk fabric was R. Lightfastness was the best at pre-Sn mordanted and the worst at Post-Al mordanted. Washing and perspiration fastnesses were improved on pre and post-Sn mordanted.