A transfer device is provided for an image forming apparatus designed such that toner images formed on a plurality of image bearing members are transferred one over another on a transfer body disposed in contact with each of the image bearing members with predetermined pressure and thus a toner image in two or more colors is formed on the transfer body. The transfer device includes a pressure varying mechanism which is capable of separating the transfer body from at least some of the image bearing members, and capable of varying transfer pressure between the image bearing members and the transfer body in contact with said image bearing members.