Disclosed is a porous polypropylene film characterized in that the air permeability change rate is low even in a high temperature environment and the initial air permeability is excellent. To achieve this air permeability, the porous propylene film is further characterized by satisfying the following conditions (1) and (2) for air permeability (Pa1) at 20°C and air permeability (Pa2) after heating for one hour at 95°C. (1) Pa1 is 800 sec/100 ml or less; (2) the air permeability change rate is 120% or less when calculated by the following equation: air permeability change rate (%) = (Pa2/Pa1) × 100.
