An image forming apparatus including a photosensitive drum unit (photosensitive unit) including a photosensitive body, a fixing unit for fixing a toner image transferred from the photosensitive body onto a recording material, and a vertical conveying path for conveying the recording material between the photosensitive drum unit and the fixing unit. Rails (guiding members) for guiding the removable photosensitive drum unit in a longitudinal direction are provided on the fixing unit. The rails are constituted of resin material capable of blocking heat transmitted towards the photosensitive drum unit.