A carbon nanobelt (CNB) is a loop of fused benzene rings and in a sense a cutout of a single-walled carbon nanotube. Various types of CNBs have been successfully synthesized in recent years and CNBs have been utilized for the development of practical devices. In this study, we investigate secondary structures formed by (6,6)CNBs and C60 molecules, which are dissolved in 1,2-dichlorobenzene. We find that uniform spherical particles are formed by (6,6)CNBs and C60 molecules in 1,2-dichlorobenzene at room temperature via bottom-up self-assembly, setting the molar concentrations of (6,6)CNBs and C60 molecules at appropriate values, and furthermore those particles are monodisperse even in water. The present facile room temperature synthetic methodology can be applied to the creation of nano/micro structures/materials using basic carbon nano units such as cycloparaphenylene (CPP, carbon nanorings) and fullerenes; e.g., C60, C70 and C59N.