To provide a method for separating and purifying nucleic acid, which has excellent separation performance, excellent cleaning efficiency and is simple and rapid, has excellent automation and miniaturization suitability and in which a porous membrane having substantially the same separation performance and being mass produced is used, especially obtaining a cleaning liquid making reduction in residual liquid amount compatible with separation performance of nucleic acid.

In the method for separating and purifying nucleic acid comprising (1) a process for passing a sample solution containing nucleic acid through a nucleic acid adsorbing porous membrane to adsorb nucleic acid on the porous membrane, (2) a process for cleaning the porous membrane in an adsorbed state of nucleic acid and (3) a process for passing a recovering liquid through the porous membrane and desorbing nucleic acid from the porous membrane, the nucleic acid adsorbing porous membrane is a porous membrane on which nucleic acid is adsorbed by interaction substantially not associated with an ionic bond and the surface tension of a cleaning liquid used is <35 mPa×m.