To compensate deterioration of an NOx reducing effect due to insufficiency of an EGR gas amount, so as to obtain a stable NOx reducing effect.

An EGR valve 10 comprises a hollow part 2 having a gas introducing port 21 and a gas drawing out port 22, valve element 3 opening/closing the gas introducing port 21, and a diaphragm part 5 for lifting the valve element 3. The valve element 3 is formed by a valve shaft part 31 connected to the diaphragm part 5 and a valve head 35 provided in a tip end of the valve shaft part 31, and formed by providing a steam injection nozzle 45 in the tip end center and a water introducing port 41 communicating with the steam injection nozzle 45 in the rear end. A conducting tube 6 for guiding water to the water introducing port 41 is connected thereto, and a water pump 61 is arranged in the conducting tube 6. A heater 7 for generating steam by heating water is provided in the inside of the valve head 35.