Interaction between single-walled carbon nanotubes (SWNTs) and a diameter-controllable supramolecule was investigated using spectroscopic and microscopic tools. Various types of cucurbit[n]uril (CB[n]), famous host molecules, were selected since their diameter can be suitably controlled and its geometric structure was well-characterized. We observed the formation of an SWNT-CB[n] complex when the SWNT was added to an acid solution of glycouril and paraformaldehyde under heating treatment and confirmed by FT-IR. The formation of the complex was visualized by field emission transmission electron microscopy. The property of SWNTs was modified by the formation of the complex, for example, enhancement in their dispersion with is promising in developing innovative nanomaterials based on SWNTs.