To operate a reformer in a high-temperature environment with reduced electric power supply to a heating element which heats a fluid migration part.

A hydrogen reforming unit 11 constituting the reformer includes a fluid migration part 20 which reforms a raw material to be reformed, a heating resistor 27 which heats the fluid migration part 20 and a vacuum container 60 which houses the fluid migration part 20. The interior of the vacuum vessel 60 (hollow part 61) is kept in a vacuum state by sucking inside air while heating the resistor 27. Consequently, the hydrogen reforming unit 11 is operated in a high-temperature environment with reduced electric power supplied to the resistor 27.