Top-contact organic field-effect transistors (OFETs) with Lewis-acid films were fabricated using copper phthalocyanine, (CuPc), and the effects of inserted Lewis-acid thin films on electrical properties were investigated. The OFETs have active layers of CuPc and vanadium pentoxide (V2O5) as a Lewis-acid film. Larger drain currents were observed for the OFET with the V2O5 layer than that without the layer. The calculated field-effect mobility of the fabricated OFET was 3.6 x 10(-3) cm(2)/(Vs), where as that of the OFET without the V2O5 layer was 2.5 x 10(-4) cm(2)/(Vs). It was thought that holes and electrons were generated in V2O5 film by gate voltage and the holes were injected into the CuPc layer. The injected holes in the CuPc layer and electrons in the V2O5 layer can contribute to drain current and the apparent high mobility.