This paper investigates the changes in export quality among ASEAN countries over time by using the economic complexity index. Specifically, we used HS 6-digit detailed trade data for 197 countries over the period from 2000-2017. The results show that the economic complexity of most ASEAN countries, except for Cambodia, Laos, and Indonesia, has improved. The export baskets of ASEAN countries are shifting from low complexity products to medium and high complexity products. We also evaluate the export quality of countries using weighted product complexity, which shows that the export quality of ASEAN countries has improved. The regression results show that economic complexity has positive effects on economic growth, and they also show that infrastructure, education level, trade openness, and financial openness contribute to the development of countries. However, the impact extent of economic complexity varies among different ASEAN countries; for example, its impact is weaker in Singapore, Thailand, and Malaysia but stronger in Vietnam, Cambodia, and the Philippines.