Infrared photodissociation spectra of (benzene-water-Ar)⁺ in the 3 μm region were observed by monitoring benzene⁺ and (benzene-water)⁺ fragments. The spectral features showed that the Ar atom locates on the benzene ring, preserving the same structure as that of (benzene-water)⁺, in which the water moiety is bound to the side of benzene⁺ by the charge-dipole interaction and C-(HO)-O-... hydrogen bonds. We evaluated the binding energy of (benzene-water)⁺ to be D₀ = 3290 ± 120 cm^-1 by analyzing the appearance energy dependence of the fragments. The binding energy of the cluster cation gave us the adiabatic ionization potential of the neutral (benzene-water) cluster, IP₀ = 72160 ± 150 cm^-1.