An intermediate transfer drum is employed and a photosensitive belt having a length equal to the outer peripheral length of the intermediate transfer drum is arranged with a vertical orientation. Developing units of the same shape are arranged on one side of the photosensitive belt, and a charging unit and a cleaner are arranged on the other side. The intermediate transfer drum is placed under or diagonally under the photosensitive belt. A transfer mechanism for transferring an image on the intermediate transfer drum to a sheet of paper is placed under or diagonally under the intermediate transfer drum. By this arrangement and construction, a small-size color electro-photographic apparatus having a size capable of easy use as a desk-top apparatus is provided, which satisfies quality of image, speed of printing, and easiness of maintenance requirements at the same time.