A porous material of a polytetrafluoroethylene (PTFE), which can retain at least 90% of 0.109 .mu.m latex spheres and has a flow rate (IPA flow rate) of at least 0.6 ml/cm.sup.2 /min as measured with isopropyl alcohol under a differential pressure of 1 kg/cm.sup.2. A process for the production of a porous material of PTFE, which comprises, after forming a molded article from fine powder of PTFE by paste extrusion, (1) sintering the molded article, (2) rolling up the molded article thus sintered and heat-treating it at a temperature lower than the melting point of the polytetrafluoroethylene in a state as rolled up, and then (3) stretching the molded article thus heat-treated in at least an uniaxial direction. The porous material of PTFE according to the present invention has micropores and good permeability and particularly is excellent in performance of retaining fine particles.

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