This experiment was conducted to investigate the effect of planting date and planting density on the growth and yield characters of yacon (Polymnia sonchifolia POEPP) and to establish cultivation method in the middle region of Korea. An introduced variety of yacon was used. Seeding dates were from April 5 to April 7,and seedlings were trasplanted three times on the May 25, june 5, and June 15 with the intervals of 10 days. Planting densities were 80(width) $ imes$ 35(distance) cm, 80 $ imes$ 45cm, and 80 $ imes$ 55cm. Plant height was not significant among planting dates, but was longer in the order of 80 $ imes$ 55cm, 80 $ imes$ 35cm, and 80 $ imes$ 35cm among planting densities. Fresh weight of top part was heavier as the planting dates were faster and planting densities were narrower. Total yeid of tuber had no significant among planting dates and was higher in the density with 80 $ imes$ 45cm and had the same tendency in the yeild of commercial goods. Correlation coefficient between plant height and yeild of commercial goods was highly positive(r= 0.927**).