The
porous membrane contains, as a main component, a
thermoplastic resin having a
melting point of 180-300 DEG C inclusive, and has a
tortoise-shell-like structure comprising a plurality of nodes and a plurality of fibrils. Alternatively, the
porous film contains, as the main component, a
thermoplastic resin having a
melting point of 180-300 DEG C inclusive, and the
compression ratio of the
porous film in the thickness direction when a pressure of 2.5 N / mm2 is applied is 20% or less. The
thermoplastic resin contains, for example, a
polymethylpentene resin. When the cross-section of the
porous film is observed, a plurality of nodes are included, for example, in the thickness direction.