This paper, based on an analysis of the Asian International Input-Output Table (1990, 1995, 2000), focuses on analyzing the structural factors in the trade interdependency among Korea, Japan, China and ASEAN. Considering the Intermediate goods structures of the four countries and the structure of the trade between them, special attention was paid to the manufacturing sectors. The manufacturing sectors were analyzed on the basis of a more detailed industrial classification than other sectors. In particular, we measured the international technological specialization (ITS) index among Korea, Japan, China and ASEAN, which provided a foundation for studying the structure of ASEAN`s heavy dependence on Korea and Japan-made intermediate inputs, but China`s dependence on ASEAN-made intermediate inputs. The ITS index shows the amount of intermediate goods that certain industries in four countries import from each other, and serves as a good indicator of the country`s dependency on imports for intermediate inputs.