This polyolefin micro-porous film includes a multilayered structure, wherein the multilayered structure contains a first layer composed of polypropylene resin, a second layer composed of polyethylene resin and provided on the first layer, and a third layer composed of polypropylene resin and provided on the second layer. Furthermore, a thickness of the first layer is thinner than a thickness of the second layer, a thickness of the third layer is thinner than the thickness of the second layer, and in the multilayered structure, a thickness is 16 μm or less, a porosity is 40 to 70%, and a surface opening ratio is 10 to 30%.