To provide an exhaust emission control system and an exhaust emission control method that reduce oxygen concentration in exhaust gas and can suitably purify exhaust gas.

The exhaust emission control system S1 comprises a granular material removing unit 12 for removing granular materials in the exhaust gas from an engine EG1 to the downstream side, a reforming apparatus 13 having reforming catalyst for producing reformed gas containing hydrogen and carbon monoxide by reacting unburned hydrocarbon component with oxygen in the exhaust gas, a three-way catalyst unit 15 having three-way catalyst acting on the exhaust gas, and a fuel/water vapor adding means 20A for adding fuel and water vapor to the exhaust gas supplied to the reforming apparatus 13.