TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The second reference temperature is set so that catalytic activity of (A) is not degraded under absence of the steam. The first reference temperature is not less than 50 - not more than 150degreesC, and the second reference temperature is not less than 300 - not more than 500degreesC.(a1) Further includes a water evaporator temperature sensor configured to detect temperature of the water evaporator. The controller includes (d1) that determines whether or not the water evaporator has a temperature at which the evaporator can generate the steam based on the temperature detected by the sensor at the start of the start-up operation of (G1). (e1) Is configured to control the supply of the water from the water supply portion to (a1), based on the determination of (d1); and is configured to start the supply of the water when (d1) determines that the temperature of the water evaporator is higher than a water evaporator reference temperature at which the water evaporator can generate the steam in determination of the determination portion.The heater is configured to heat (a1) when (d1) determines that the temperature of the water evaporator is not higher than the water evaporator reference temperature. (d1) Is configured to start a third determination process (P3) in such a manner that the determination portion compares the temperature of (A) which is detected while (a1) is heated after (P1) to a third reference temperature which is higher than the first reference temperature and lower than second reference temperature, when (d1) determines that the temperature of (A) is not higher than the first reference temperature in (P1).The heater is configured to stop the heating of (a1) when (d1) determines that the temperature of (A) is higher than third reference temperature in (P3), and (d1) performs a fourth determination process (P4) in such a manner that (d1) compares the temperature of (A) after the stop of the heating to a fourth reference temperature which is lower than third reference temperature and higher than first reference temperature.The heater is also configured to re-start the heating of reformer when (d1) determines that the temperature of (A) is lower than fourth reference temperature in (P4). The third reference temperature is not less than 200 - not more than 300degreesC. The heater heats (a1) so that the temperature of (A) becomes higher than third reference temperature, after stop and re-start of the heating of (a1) which is performed at least once, or after the heating of (a1) involving the stop and the re-start is performed for a predetermined time period where (e1) is configured to start the supply of the water when (d1) determines that the temperature of (A) is higher than the second reference temperature in (P2).The controller decides the times the stop and the re-start of the heating are performed or the time period for which the heating involving the stop and the re-start is performed, according to the temperature of (A) detected at the start of the start-up operation of (G1). (a1) Further includes a water evaporator temperature sensor to detect temperature of the water evaporator. The water evaporator reference temperature is not less than 50 - not more than 150degreesC. The water evaporator is located at outermost portion of (a1) and (A) is located inward relative to the water evaporator.The heater includes a burner to combust a combustion fuel and air; a fuel supply portion to supply the combustion fuel to the burner; and an air supply portion configured to supply the air to the burner. (a1) Is configured to exchange heat between a combustion exhaust gas generated in the burner and (A) and then between the combustion exhaust gas and the water evaporator. (e1) Is configured to control supply of air from the air supply portion to a burner of the heater; and to supply air to the burner at a second flow rate when (d1) determines that the temperature of (A) is not higher than the first reference temperature in (P1). The air supply portion supplies air to the burner at a first flow rate after (c1) starts the supply of water.The ratio of the first flow rate to a theoretical air amount in complete combustion of the combustion fuel in the combustion is performed with the air supplied at the first flow rate is smaller than ratio of second flow rate of the theoretical air amount in complete combustion of the combustion fuel in combustion performed with the air supplied at the second flow rate (preferably not less than 2).(e1) Is configured to inject the air from the air supply portion to burner of the heater in a heating stop period during which the combustion in the burner is stopped according to determination of (P3); and is configured to start the supply of the material from (b1) after an elapse of a predetermined time after the start of the water supply according to determination in (P1) or after an elapse of a predetermined time after the start of the water supply according to determination in (P2). The water is reserved in the water evaporator before the temperature of the water evaporator becomes a temperature at which the water evaporator can generate the steam.