This paper aims at analyzing the virtual water balance within the Asia-Pacific region. For this purpose, we construct a multi-country multi-sectoral model which is based on international input-output tables in constant prices and local currencies. The results on the virtual water balance within the region show that Indonesia, the Philippines, Thailand, China, and the United States are exporters whilst Malaysia, Singapore, Taiwan, South Korea, and Japan are importers. Employing the model, we also quantify the effects of population aging in China on the virtual water balance within the region. The virtual water balance decreases in China whereas it increases in most sectors of the other economies. One of the exceptions is the agricultural sector in the United States. In this sector, water use embedded in exports greatly decreases due to the deterioration of the U.S. price competitiveness. Water embedded in domestic demand also decreases because of the fall in China's demand. Since population is definitely aging in the Asia-Pacific region other than the United States and aging itself is negatively correlated to the agricultural consumption, the results imply that population aging has potential to substantially change the level and composition of the U.S. virtual water balance.