The present invention provides a thermoelectric conversion material of which the structure is controlled to have nano-order microscopic pores and which has a low thermal conductivity and has an improved thermoelectric performance index. In the thermoelectric conversion material having a thermoelectric semiconductor layer formed on a block copolymer substrate that comprises a block copolymer having microscopic pores, wherein the block copolymer comprises a polymer unit (A) formed of a monomer capable of forming a homopolymer having a glass transition temperature of 50° C. or higher, and a polymer unit (B) formed of a conjugated dienic polymer.