We successfully synthesized an amphiphilic pyrrole derivative, 12-pyrrolyl dodecanoic acid (PDA) and fabricated the Y-type multilayer PDA Langmuir-Blodgett (LB) films by the conventional vertical dipping method. We, however, could not obtain an electroconductive polymer LB film from PDA alone. We, therefore, carried out in situ copolymerization of pyrrole and PDA at the air-water interface by spreading the mixture solution of pyrrole and PDA with various feed ratio in chloroform onto a subphase containing 1 wt.% FeCl3. We confirmed that the well ordered electroconductive Y-type poly(PPy-co-PDA) LB film was successfully prepared with the feed mole ratio of 300:1 (pyrrole:PDA) under the condition of surface pressure 33 mN/m, pH 5.3, and 17 ℃. Poly(PPy-co-PDA) LB multiplayer film showed the fairly high electrical conductivity of 2.3×10 (-3)S/cm and extremely smooth surface. We expect the electrically conducting polymer film with good structural order can be applied to many potential application fields such as volatile organic sensor, biosensor, or surface acoustic wave devices.