Concentration of microwave alkali pretreated wheat straw hydrolyzate to increase sugar concentration was carried out by evaporation in rotatory evaporator (a type of vacuum distillation unit) and the boiling temperature of the liquid was maintained at 80 ◦C. Water (and compounds with low boiling point) evaporated from the hydrolyzate and amount of the hydrolyzate was reduced to 1/3 of the original amount.