The relationship between Korean FDI and trade to Southeast Asian countries depends on the types of trade. According to empirical study, although FDI increases her intra-industry trade to Southeast Asian countries, it decreases her inter-industry trade to them. The results are consistent to the international trade theories. The empirical results also show that Korean trade to Southeast Asian countries increases as her and their economic size get larger. Especially horizontal intra-industry trade responds positively to economic size shock. It is also found that Korea trades more with smaller countries rather than bigger countries in Southeast Asia. In addition, trade volume between Korea and Southeast Asian countries expands as their average per capita GDP increases. it is also found that Korea trades more with similar countries in the level of economic development. The most results are consistent to the intra-industry trade theories. But the results above depend on types of trade, horizontal intra-industry trade or vertical intra-industry trade.