Field-effect transistors (FETs) using charge-transfer (CT)-complex Langmuir-Blodgett (LB) films were fabricated and their FET characteristics were measured. Four-layer (2 bilayers), 3-layer (a bilayer and a monolayer) and monolayer of Y-type TMPD-CnTCNQ LB films were examined as active layers of the FET. The FET characteristics strongly depended on the number of CT-complex layers. The monolayer FET showed the highest dependence of drain-source current (IDS) on gate voltage (VG) although the film was the least conductive among the three. Elimination of bilayer units, of which the structure is symmetric against the substrate normal, was concluded to be essential for improving the VG dependence. The cutoff frequency of the CT-complex FET was estimated to be 5 Hz.