Having silk dyed with some pigment extracted from the skin of an onion, examined the change of color by time and frequency of dyeing and a mordanted cloth, and the antibiosis of a dyed cloth and a mordanted cloth. The result of this were as follows ; 1. The pigment of an onion was easily extracted in the hot water of $40^{circ}C$ and much more extracted as the temperature of water rises($70^{circ}C$). 2. As a result of dyeing it by the change of time, 30minutes, 60minutes, 90minutes and the frequency of dyeing, once, twice, three times after filtering the extracted solution, the one dyed three times for 30minutes was the best. 3. The difference of color of a mordanted cloth was the highest in the mordant of $SnCl_2;2H_2O$ on the basis of the value of L of the non-mordant dyed three times. 4. The mordant of copper sulfate was proved to have the highest antibiosis in the antibiosis of a dyed cloth and a mordanted cloth, and it was proved that the pigment of the skin of an onion had excellent antibiosis.