The recent trend of sea level rise in the East/Japan Sea (EJS) is investigated using TOPEX/POSEIDON (T/P) altimetry, long-term tide gauges and thermosteric sea levels (TSL) at stations where long term temperature data are available. The T/P analysis reveals an EJS-averaged increase of about 5.7±0.1 mm/yr over 9 years, 1993-2001, which is much larger than the global rate of 3.1±0.4 mm/yr reported by Cabanes et al. (2001). This increasing rate is relatively well compared with those by tidal sea level and thermosteric sea level. The EJS reveals non-uniform patterns of sea level change, with two regions, the western part of the Ulleung and Yamato basins, having values of 10 mm/yr and larger. The possible cause of this large increase is discussed in terms of thermal expansion and recent large decadal trend of temperature anomaly by eddy stability in the upper layer of the Ulleung and Yamato basins, as shown in Kang et al. (2004). Analyses of 40-year long TSL reveal a decadal oscillation at the Ulleung and Yamato basins, due to temperature variations in the 300-m thick upper layer. Most of TSL stations show such oscillations, even though the decadal trend in some of them is weak. This oscillation is apparently related to the decadal variation of heat content in the upper 300 m of the Pacific Ocean, reported by Levitus et al. (2000).