<p>[PROBLEMS] To provide a porous polymer film which can keep its high filtration ability and can exhibit its fractionation property when the film is used to carry out a cross-flow operation in a solution containing a biological component. [MEANS FOR SOLVING PROBLEMS] Disclosed is a porous polymer film having a structure composed of polymer microparticles and a microfibril that links the microparticles to each other. The porous polymer film has discrete depressed parts located in the length-wise direction on a surface that contacts with a solution to be treated. The depressed parts are located on the surface at a ratio of 10 to 30% inclusive. The depressed parts have an average width in the width-wise direction of 0.05 to 0.12 µm inclusive, and an average length in the length-wise direction of 0.10 to 0.50 µm inclusive.</p>
