An image forming apparatus that sets a second conveyance speed, at which a recording material is conveyed at a heating nip portion, higher than a first conveyance speed, at which the recording material is conveyed at a transfer nip portion, conveys an envelope by the transfer and heating nip portions without transferring a toner image at the transfer nip portion. After that, the image forming apparatus which sets the second conveyance speed equal to or lower than the first conveyance speed transfers the toner image formed on a photosensitive drum acting as an image bearing member onto the envelope conveyed again to the transfer nip portion by a reversing conveyance mechanism acting as a re-conveyance unit to fix the toner image on the envelop at the heating nip portion.