The present invention provides an asymmetric porous PTFE membrane for a filter having little change over time and conventionally known properties of a porous PTFE molded article such as water permeability resistance, air permeability, sealing properties and electric properties, in which collection efficiency, air permeability and pressure loss are improved. Specifically, the present invention relates to an asymmetric porous PTFE membrane for a filter comprising a dense skin layer and a continuously foamed porous layer, wherein (1) the contact angle of water to the surface of the skin layer is 120 to 140.degree.; and (2) the diffuse reflectance of light is 91 to 94%.