To obtain an antithrombotic porous membrane which can be efficiently produced and has high anti-thrombogenicity and a hydrophobia porous membrane surface and to provide a method for producing the antithrombotic porous membrane.

This antithrombotic porous membrane is characterized in that a high molecular-weight hydrophilic polymer having 500,000-1,500,000 weight- average molecular weight and a low molecular-weight hydrophilic polymer having 10,000-10,000 weight-average molecular weight exist on the surface of a porous membrane which is formed by using a hydrophobic polymer and with which blood is brought into contact. The method for producing the antithrombotic porous membrane is also provided.