A duplex scanning apparatus includes an automatic document feeder and a flatbed image scanner. The automatic document feeder includes a document feeder case, a scanning glass plate and a first light source. The flatbed image scanner includes a scanner case, a glass platform, a second light source and a scanning module. The scanning glass plate and the first light source are included in the automatic document feeder of the duplex scanning apparatus, so that the scanning operation is performed in the automatic document feeder.