Non-chemically treated single-walled carbon nanotubes (SWCNTs) were assembled at a liquid-liquid interface in the shape of an ultrathin film. SWCNTs were dispersed into water phase by aid of sodium dodecyl sulfate (SDS) and were assembled at a hexane-water interface with addition of ethanol. The assembled film was transferred onto a solid substrate at various dipping speeds. Polarized absorption spectra of the transferred film indicated that the SWCNTs aligned with their long axis parallel to the dipping direction when the assembly was transferred at the dipping speed of 50mm/min.