In order to investigate mixing in the Ulleung Basin in the East Sea, the Korea Ocean Research and Development Institute conducted a hydrographic survey which included turbulence measurements using the R/V Eardo in September 2006 and March 2007. In 2006, a small warm eddy characterized by homogeneous 10° C water appeared at 100 - 200 m depth in the region southwest of Ulleungdo. Sea surface temperature was lower near the coast of Dok Island (Dokdo) compared to the outer area, indicating mixing near the island in March 2007. Microstructureprofiling measurements were carried out at 26 stations in the Ulleung Basin and at 10 stations between Ulleungdo and Dokdo, respectively. The dissipation rate of turbulent kinetic energy (ε) is used to estimate the diapycnal eddy diffusivity. The largest value of ε, 1×10-5 Wkg-1, appears in the surface layer. The stability in the thermocline is very strong, even though it takes much more energy to displace a particle of water. It is characterized by a high value of the Brunt-Väisälä frequency, 1×10-4 s-1, and high ε in the thermocline is measured. This high ε in the thermoclineseems to be caused by internal waves. Higher eddy diffusivity of 5×10-3 m2 s-1 is calculated at a station near Dokdo which probably results from the island effect of Dokdo.