To improve fuel economy, increase output and make exhaust gas components clean by improving combustion efficiency of an internal combustion engine.

Exothermic reaction of ethanol fuel and air supplied from an air supply device 46 is performed on a fuel reforming device 24 during start of the internal combustion engine 12, and heat (reformed gas) generated by the exothermal reaction is led out to an exhaust side three-way catalyst 20 via a three-way change over valve 32 and a second circulation passage 34 to warm up the three-way catalyst 20. Endothermic reaction of ethanol fuel, steam and heat in exhaust gas circulated by an exhaust gas circulation passage 28 is performed on the fuel reforming device 24 during normal travel, and reformed gas containing hydrogen formed by the endothermic reaction is sent to the internal combustion engine 12 along a first recirculation passage 26 under a change over action of the three-way change over valve 32.