PURPOSE: To improve reliability in sensing of the presence or absence of flames by providing an electromagnetic wave sensor directing to the flames of a pilot burner for igniting burners for heating the interior of a reforming furnace and sensing the presence or absence of the flames.

CONSTITUTION: The subject reformer 1 is formed from a reforming furnace 5, a combustor 4 for heating the reforming furnace 5 to a prescribed temperature, an electromagnetic wave sensor 21, etc. The aforementioned combustor 4 is provided with main burners 8 and a pilot burner 7 for igniting the main burners 8. The above-mentioned sensor 21 is installed to direct to flames 9 of the aforementioned pilot burner 7 and electromagnetic waves produced from the flames 9 are sensed to sense the presence or absence of the flames 9.