This experiment was conducted to investigate the change of root yield and essential oil contents by cultivated year in Asaram siebold Mio. Growth of aerial part such as plant height, leaf length and leaf width increased rapidly in two to three-year-old. Root length and root weight per plant were increased as cultivation year passed. Especially the speed of development was very fast in two and three-year-old alike aerial part. Root yield was the highest at five-year-old. The content of essential oil was decreased gradually as cultivation year passed. Methyleugenol content was increased, while safrole content was decreased by cultivated years. The increasing of methyleugenol content in four to five-year-old was not higher than three to four-year-old. In the result, it concluded that the optimum harvest time of Asarum sieboldi MiO is five-year-old cultivated based on root yield and effective medical components.