NOVELTY - Reforming system comprises reforming apparatus (2) having reformer (34) for generating reformed gas containing hydrogen by reacting gaseous raw material for reforming with water. An inlet-side valve (25a, 25b, 25d, 25m) supplies the gaseous raw material for reforming to the reformer of the reforming apparatus. An outlet-side valve (25e, 25h) discharges the reformed gas being generated at the reformer of the reforming apparatus out of the reforming apparatus. A controller (500) controls the inlet-side valve and the outlet-side valve.    USE - Reforming system for generating reformed gas, which contains hydrogen, by reacting gaseous raw material for reforming with water.    ADVANTAGE - The reforming system is capable of inhibiting inner pressure of reforming apparatus from increasing excessively, which can be made without ever setting the pressure resistance of reforming apparatus superfluously high.    DETAILED DESCRIPTION - Reforming system comprises a reforming apparatus (2) having a reformer (24) for generating reformed gas containing hydrogen by reacting gaseous raw material for reforming with water. An inlet-side valve (25a, 25b, 25d, 25m) is disposed on an upstream side with respect to the reforming apparatus, to supply the gaseous raw material for reforming to the reformer of the reforming apparatus. An outlet-side valve outlet-side valve (25e, 25h) is disposed on a downstream side with respect to the reforming apparatus to discharge the reformed gas being generated at the reformer of the reforming apparatus out of the reforming apparatus. A controller (500) controls the inlet-side valve and the outlet-side valve. When the controller carries out reforming-operation turning-off procedure after operating the reforming apparatus, the controller carries out closing procedure for closing both the inlet-side valve and the outlet-side valve. The controller carries out opening/closing procedure in which the controller not only maintains the inlet-side valve's closed state but also opens the outlet-side valve when pressure inside the reforming apparatus increases to predetermined pressure, and then closes the outlet-side valve. It flows gas for cooling into the heater of the reforming apparatus.    DESCRIPTION OF DRAWING(S) - The drawing is a block diagram of the reforming system.    Reforming apparatus (2)    Inlet-side valve (25a, 25b, 25d, 25m)    Outlet-side valve (25e, 25h)    Reformer (34)    Controller (500)