As the economic and political importance of ASEAN has grown significantly in East Asia in recent years, China has been making substantial efforts to strengthen its relationship with ASEAN, reshaping the regional order. This paper first examines China's active approach toward ASEAN in recent years with a focus on economic and security cooperation, and analyzes China's objectives in it and potential obstacles that China may face. Second, this research studies the impacts of China's recent approach toward ASEAN on neighbor countries, in particular South Korea. This paper argues that China's efforts to strengthen its relations with ASEAN has an adverse effect on South Korea's foreign economic policy toward East Asia and that they may place the country in an uneasy strategic position between China and the United States and also between China and Japan.