PURPOSE: To facilitate the production of a porous fluorocarbon resin membrane having excellent chemical resistance and a extremely large pore diameter, by dissolving a solvent-soluble polymer containing a vinyl fluorocarbon resin and a pore forming agent in an organic solvent, removing the solvent from the solution and stretching the membrane.

CONSTITUTION: A solvent-soluble polymer containing at least one vinylic fluorine-containing compound and a pore forming agent are dissolved in an organic solvent. The resulting solution is desolvated in an atmosphere containing this organic solvent and the membrane is stretched at a ratio ≥1.2, to obtain a porous polymer membrane containing the pores with a shape of an ellipse having a major axis of 1W50μm and an average major axis which is 1.5 times the average minor axis. The above polymers which can be suitably used include polyvinyl fluoride or copolymers of vinylidene fluoride with tetrafluoroethylene or propylene. The porosity of the porous membrane is preferably 20W85%.