PURPOSE: To prevent a developer from scattering owing to transfer by providing a conductive base material and an insulating layer which is superposed on the conductive base material on a side where a developer image is transferred.

CONSTITUTION: A transfer belt 12 consists of the conductive base material 6 with conductivity and the insulating layer 7 which is formed thereupon and at a transfer position of an (n)th image formation unit U, a toner image 4a is transferred by an electrostatically charged transfer material 10 on the transfer belt 12 to form a composite toner image 22. Consequently, potential differences between the transfer position of the developer image and transfer materials which are placed before and behind it can be made small to obtain a superposed image without scattering the developer image owing to transfer. Further, the conductive base material 6 has preferably ≤1010 Ωcm conductivity and the insulating layer 7 has preferably ≥1013 Ωcm insulating property.