Rice husk is one of the important biomass feedstocks which can be a raw material of chemicals products as well as the energy source. In this work we focused on furfural production from rice husk. It is known that furfural can be produced from pentoses that exist in rice husk; however, the undesired secondary decomposition of furfural thus obtained easily occurs to decrease the furfural yield because of its high reactivity. It is necessary to control such undesired side reactions. To solve such a problem, we have developed a membrane reactor system in which hydrothermal reaction and pervaporation occur simultaneously (reactive pervaporation) and shown its efficiency based on a series of experimental data using some model compounds and its mathematic analyses. In this presentation, the results of reactive pervaporation for an existing biomass, i.e., rice husk, are shown.