We studied the spatio-temporal characteristics of the Ullung Warm Lens (UWL) using the historical oceanographic data of the National Fisheries Research and Development Agency of Korea in the East Sea from 1967 to 1983. The UWL is basically a subsurface phenomenin found in 100 to 300m depths, and its existence is not well posed in the distribution of the sea surface temperature. The UWL has a typical size of 100 km diameter, and its center migrates within the region of 150 by 150 km south of the Ullung Island. The UWL is almost a permanent feature, and the probability of its occurence within our study area ($129~132^{circ}E,;36~38^{circ}N);was;86\%$.