The noncatalytic decomposition characteristics of cellulose in near-critical water were examined by heating a sealed reactor in which the cellulose and water were charged in a salt bath kept at 305, 355, or 405 degrees C. Cellulose was rapidly decomposed to water solubles (WS), and the WS was further decomposed after the WS yield reached nearly 80%. The heating time giving the maximum WS yield was shortened to under 15 s by increasing the treatment temperature to over 355 degrees C. In the WS formation process, hydrolysis preferentially occurred, and the glucose yield reached 40% by the treatment for 15 s in the bath kept at 355 degrees C. On entering the second decomposition process, the WS was converted to gaseous products and methanol-soluble products, and char-like solid products were formed from the liquid phase. The hydrolysate of cellulose obtained in the WS formation process was subjected to a fermentation test, and the formed glucose was confirmed to be converted to ethanol.