PURPOSE: To facilitate the production of a two-layer type porous film having excellent strengths and high moisture permeability.

CONSTITUTION: This production process comprises melt-molding (for example, extrusion molding with a two-layer die C) material X1 prepared by mixing a base material comprising a fluororesin (e.g. ETFE) with a VdF copolymer and a fine hydrophilic inorganic powder in a specified ratio and material X2 prepared by mixing a base material comprising a fluororesin (e.g. ETFE) with a VdF copolymer in a specified ratio to form a two-layer film 1' and extracting the above VdF copolymer from the two-layer film 1' to obtain a two-layer porous film 1 composed of a hydrophilic layer 1a and a hydrophobic layer 1b.