Supramolecular composites composed of fullerene C60 and carbon nanodiamond (ND) were constructed through spontaneous complexation of C60 aggregates onto the surface of ND aggregates in N‐methylpyrrolidone (NMP). The resulting C60‐ND composite was assembled onto a nanostructured SnO2 electrode by an electrophoretic deposition method. Formation of the C60‐ND composite was confirmed by dynamic light scattering (DLS) and field‐emission scanning electron microscopy (FESEM). The C60‐ND composite on the SnO2 electrode showed high incident photon‐to‐current efficiencies (IPCEs) in the visible region as compared with the single component system of C60 or ND. The improved photocurrent generation of the C60‐ND composite may result from the photoinduced charge separation at the interface between C60 and ND. These results obtained here will provide valuable information on the design of optoelectronic devices based on all‐nanocarbon materials.