It has been shown that the conjugated polymer films for electronic devices can be prepared by the electrophoretic deposition with polymer suspensions derived from dilute polymer solutions which are so dilute that the conventional spin-coating technique is not applicable. For example, a few hundreds nm-thick film can be prepared on an indium-tin-oxide electrode from a suspension derived from a solution containing 0.1 g/L of the polymer. The polymer light-emitting devices with various thickness of the emission layer prepared by the electrophoretic deposition have been demonstrated.