Ethanol fermentation of lignocellulosic biomass, which is now attracting much of attention all over the world, is one of ways to produce renewable and alternative fuel. However there are many kinds of lignocellulosic biomass, therefore we have to take account of structure differences among each lignocellulose. In our experiments, three kinds of lignocelluloses were treated in hydrothermal conditions followed by cellulase hydrolysis. By analyzing the results in terms of reaction engineering, it was found that each material have different reactivity in hydrothermal condition from others. It can be assumed that the difference of reactivity caused by the difference of cell wall structure.