Infrared and electronic spectroscopy was applied to the benzene-ammonia cluster cation in the gas phase, and the observed spectra revealed the formation of a new C-N valence bond between the benzene and ammonia moieties, which has been predicted by the quantum chemical calculations (Tachikawa, H. Phys. Chem. Chem. Phys. 2002, 4, 6018). This cluster cation is regarded as a model for the cyclohexadienyl type intermediate in nucleophilic substitution reactions.