A module for transferring a substrate includes a load port for supporting a container to receive a plurality of substrates, a substrate transfer chamber disposed between the load port and a substrate process module, a substrate transfer robot disposed in the substrate transfer chamber for transferring the substrates between the container and the substrate process module, a gas supply unit connected to the substrate transfer chamber for supplying a purge gas into the substrate transfer chamber to purge an interior of the substrate transfer chamber, and a contamination control unit connected to the substrate transfer chamber for circulating the purge gas supplied into the substrate transfer chamber, resupplying the circulated purge gas into the substrate transfer chamber and removing particles and airborne molecular contaminants from the purge gas being circulated. Contamination of a substrate may be prevented and a necessary amount of purge gas may be reduced.