A precise electrically conductive circuit was fabricated on a plastic film substrate with an electroless Cu-plating layer that was formed on a metal colloid printed pattern. The printed pattern was formed with the inks that contain the mixture of silver colloid and palladium colloid. The degree of catalytic activity of the printed pattern upon the electroless Cu-plating was enhanced by the addition of an extremely small amount of palladium colloid into the metal colloid ink; plating speed was increased by the three times on the metal colloid pattern that was formed with the inks containing only 1 wt% of mixed metal colloids. The Electronic circuit formation and its practical performance were confirmed for the circuit fabricated by both PIJ (Cu-plating on ink jet pattern) and PFS (Cu-plating on filled and squeezed pattern) processes.