An image forming apparatus includes a photosensitive body on which a visible image is developed by developer, an intermediate transfer belt to which developer of the photosensitive body is transferred, and a first transfer roller to transfer the developer from the photosensitive body to the intermediate transfer belt, wherein since a developing unit housing at which the photosensitive body is mounted is provided with position regulating guides to support a shaft of the first transfer roller, the intermediate transfer belt comes into contact with the photosensitive body at a uniform angle. As a result, uniform print quality may be obtained.