In order to develop a new process for the production of polylactic acid by adopting rice as material, it is important to find the optimal operational conditions to produce lactic acid as much as possible. In this work, effective liquefaction and saccharification of starch were investigated for the lactic acid fermentation. The states of a sample under the pretreatment were roughly evaluated by measuring the power consumption of an impeller to agitate a solution and the molecular weight of starch.