Rice straw was treated under hydrothermal condition for producing furfural, which is one of the degradation products of hemicellulose. The highest furfural yield (19.6 mg/g-rice straw) was obtained at 220°C for 15min under hydrothermal condition. Main product was furfural, but the other oxygenated compounds, such as acetic acid and formic acid, were also obtained at this condition. When the phosphoric acid solution was added to the compressed water, the yield of furfural increased remarkably, and the highest yield (26.0 mg/g-rice straw) of the furfural was obtained at 220 °C for 15min. It is shown that addition of phosphoric acid solution to the compressed water provided the higher yield to obtain the furfural from rice straw.