The present invention provides a method for producing a porous base material having a pore with a surface modified, the method being unlikely to limit a material of the porous base material and being suitable for controlling characteristics of the porous base material by introducing a polymer chain into a surface of a pore of the porous base material while inhibiting a change in a structure of the porous base material itself. The production method of the present invention includes: forming a base layer having a polymerization initiating group in such a manner as to cover a surface of a pore of a porous base material; and allowing a monomer group to be in contact with the base layer and thereby polymerizing the monomer group by the polymerization initiating group.