Geochemical data on TOC (total organic carbon), elements (C, H, N, S), headspace gas, carbon isotope (d¹³C) and interstitial water were determined in total 28 piston cores from the Ulleung Basin of the East Sea (Sea of Japan), representing late Pleistocene and Holocene. The results show that TOC is almost more than 0.5%, and the headspace gases consist predominantly of CH4, which ranges from 0.00 ml/l wet sediment to 87.40 mL/L wet sediment. In particular, the content of headspace gas has a high value in 00GHP cores. The headspace gas is thought to be of biogenic origin rather than thermogenic, because its carbon isotopic composition has a low value, ranging from -78.04‰ to -55.50‰. In addition, the void structure was observed in 00GHP and 01GHP cores, which probably resulted from the gas expansion. Compared to the variation between the sulfate of the interstitial water and CH4 in 01GHP-05 and 07 cores, relative concentration of the sulfate tends to decrease with increasing of burial depth, whereas CH4 shows an increasing trend. This implies that the sulfate reduction changed gradually into the methanogenesis as burial depth increases.