An image forming apparatus for recording on two sides in a single pass, with which the transfer of a toner image onto one side of a recording medium and the transfer of a toner image onto the other side can both be performed under optimal conditions, which results in an increase in image quality. Contact-type transfer rollers are used as secondary and tertiary transfer means, so unlike with a transfer charger (a non-contact type of transfer means), there is no discharge product. A toner image that has been once transferred from an image support onto a recording medium is prevented from being retransferred back onto the image support, and a toner image that has been transferred onto the recording medium by the action of a first transfer member is prevented from being retransferred to the image support when a toner image is transferred onto the recording medium by the action of a second transfer member.