A developing unit of a liquid electrophotographic printer includes a developing roller, for forming a development gap with a photoreceptor web where developer is filled and developing an electrostatic latent image formed on the photoreceptor web, a squeegee roller installed at the rear end of the developing roller for closely pressing the photoreceptor web to squeegee surplus developer, and a cleaning mechanism for removing toner particles of the developer adhering to a surface of the squeegee roller using an electrical force. Since the toner particles adhering to the squeegee roller are removed, contamination of a developed image is prevented and a clean image can be printed.