Thermoelectric conversion is one of the key technology to develop a battery for wearable device. Recently, single-walled carbon nanotubes (SWNTs) have attracted much attention as substitutes due to their lower cost, ease of fabrication, flexibility, light weight and large Seebeck coefficient. While SWNTs are promising p-type organic thermoelectric materials, the development of the flexible n-type thermoelectric materials is still challenging even at present, because n-type semiconducting organic materials are inherently unstable in air due to oxidation. In this study, we developed n-type SWNT sheet by doping of small molecules.