We studied the charge-transfer (CT) interaction between poly(9-vinylcarbazole) (PVK) and 3,5-dinitrobenzamido (DBA) group or 3-nitrobenzamido (NBA) group. The complexation equilibrium constant of PVK and N-butyl-3,5-dinitrobenzamide was found to be larger than that of PVK and N-butyl-3-nitrobenzamide using UV-vis spectroscopy. The desorption process of PVK from a DBA-modified substrate was studied with single molecule force spectroscopy. A lot of force-extension curves with a plateau were observed, which indicated the existence of trainlike conformation. The average desorption force of a PVK chain from the DBA-modified substrate was 28 pN. For comparison, the desorption process of PVK from an NBA-modified substrate was also studied, and an average desorption force of 18 pN was obtained. The apparent interaction energy of a CT complex was calculated on the basis of the desorption force and the surface density of electron acceptors. The obtained apparent interaction energies were 14 and 8 kJ x mol(-1) for the carbazolyl-DBA complex and carbazolyl-NBA complex, respectively. On the basis of the energy of the frontier molecular orbital of carbazole, 3,5-dinitrobenzamide, and 3-nitrobenzamide, the difference in strength between the interactions was interpreted as the influence of the substituent group on the energy of the frontier molecular orbital.