Structural and electrical properties of the Cu-In binary system have been studied in thin films. Samples were prepared via sequential vacuum deposition and annealing. Copper of 10-40 nm thick was deposited on glass substrates first, and indium deposition was followed. The In thicknesses were chosen so as to make the atomic concentration of In 0-75%. Physical properties became stable after annealing at 120 degrees C for 10 min. The X-ray diffraction pattern of the alloy film exhibited the C16 structure near the 65 at.% In, suggesting the formation of the intermetallic compound CuIn2. Electrical properties of films were evaluated with Hall measurement. The resistivity of the ahoy film increased with In concentration, had a maximum at similar to 35 at.%, then decreased and showed a minimum at similar to 65 at.%, reflecting the CuIn2 formation. Hall coefficient of alloy films was naturally negative at low concentrations of In. However, the value gradually decreased to zero with the increase in In content and finally became positive above 40-50 at.% of In. From the temperature dependence of these electrical properties in the alloyed films, the co-existence of the 'hole'-like and 'electron'-Iike electron orbits has been speculated.