A spray drying system for drying wastewater to be dried includes: an exhaust as introduction line for introducing the exhaust gas discharged from an exhaust gas generation source, the exhaust gas introduction line being connected to a plurality of exhaust gas ducts for allowing the exhaust gas to flow through; and at least one spray drying device connected to the exhaust gas introduction line and configured to bring the exhaust gas introduced from the exhaust gas introduction line into contact with the wastewater. The number of spray drying device is smaller than the number of the plurality of exhaust gas ducts.