To improve engine combustion and to reduce exhaust gas efficiently.

An evaporator 41 gasifies a mixed liquid passing through its internal heat exchange pipe 41a by making the mixed liquid absorb exhaust heat and supplies fuel mixture to a reformer 43 through a pipe 42. The reformer 43 performs steam reforming on the fuel mixture by means of a catalyst to generate fuel mixture including hydrogen, carbon dioxide and a slight amount of carbon monoxide and supplies reformed gas to a hydrogen separator 45 through a reformed-gas pipe 44. The hydrogen separator 45 separates the hydrogen from the reformed gas and supplies the hydrogen to an intake pipe 21 through a hydrogen supply pipe 46 and a hydrogen supply valve 50.