<;P>;PROBLEM TO BE SOLVED: To provide a method for refining a recombinant protein hard-to-be extracted from a recombinant plant. <;P>;SOLUTION: The method for refining a hard-to-extract recombinant protein expressed in a recombinant plant by extraction using an extractive solution containing a reducing agent and a surfactant or an extractive solution containing n-propanol and &beta;-mercaptoethanol, is provided. <;P>;COPYRIGHT: (C)2010,JPO&INPIT