The plant growth and yield of Pinellia ternata (Thunb.) Breit. were studied by altitude and tuber weight. The emergence rates in low land area were not different by tuber weights, but it showed earlier emergence date in heavier weight of seed-tuber and low land area. The higher aerial growth such as plant height and number of leaves per plant was the heavier tuber weight in a planting year, but the growth was not different by the weight of tuber at second year after planting. The distribution pattern of tuber size per $m^2$ was not influenced by different seed-tuber weight. The number of harvested tuber was highest at more than 1 g of tuber weight, and followed 1~2 g and less than 2 g. The distribution pattern of fresh tuber yield was not influenced by different altitude and seed-tuber weight. The marketable tuber, 2 g or more, tends to be produced with more than 0.6 g seed-tuber. As the results above-mentioned, it was thought that the high yield was supposed to use seed-tuber over 0.6 g in the fertile soil.