The present invention provides: a thermoelectric conversion material which has low thermal conductivity and improved thermoelectric performance index; and a method for producing the thermoelectric conversion material. A thermoelectric conversion material that is obtained by forming a thermoelectric semiconductor layer, which is a film formed from a thermoelectric semiconductor material, on a substrate that has a nanostructure with micropores of nanometer order. The substrate is a block copolymer substrate which is formed of a block copolymer that is configured of a polymethyl methacrylate unit and a polyhedral oligomeric silsesquioxane-containing polymethacrylate unit. The thermoelectric semiconductor material is a p-type bismuth telluride or an n-type bismuth telluride. A method for producing a thermoelectric conversion material, which comprises: a substrate formation step wherein a block copolymer substrate having the above-described nanostructure is formed; and a film formation step wherein a thermoelectric semiconductor layer is formed by forming a film from a p-type bismuth telluride or an n-type bismuth telluride.