Although liquid development using submicrometer-sized toner particles is suitable for achieving high image quality including half-tone images, conventional liquid developing units are limited in speed and cause chemical pollution. Furthermore, the need for a built-in toner density control unit makes the printer equipment complex. To solve these problems, a liquid developing unit using highly concentrated liquid toner that can develop the latent image in a small developing area without any toner density control is available. This unit contains a developing roller that also works as a filming roller and squeezing roller. Optimal developing conditions that yield a high-quality image with a noise-free background are described.