Reactor

A reactor comprising

• a reaction vessel having an inlet for a to-be-reformed gas and an outlet for a reformed gas,
• a pair of electrodes for plasma generation, disposed in an internal space of the reaction vessel so as to face each other,
• a power source for applying a voltage to the pair of electrodes, and
• a catalyst for promoting reforming reaction of the to-be-reformed gas,
• wherein
• one of the pair of electrodes is a linear electrode,
• the other of the pair of electrodes is a honeycomb electrode made of a conductive ceramics having a plurality of cells to act as gas passages partitioned by partition walls, and
• the catalyst is loaded on the partition walls of the honeycomb electrode,
• the reactor further comprising
• shielding members protruded from a gas-introducing end face of the honeycomb electrode in a space between the linear electrode and the honeycomb electrode to prevent the to-be-reformed gas passing through a zone other than a plasma-generating zone from flowing into the honeycomb electrode.