TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The bonding part is made of a metal having a melting point lower than the melting point of a material of the reaction plate and the cover plate, and comprises a brazing material.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Reformer: The reaction plate Has a first portion that defines an area of the channel, and a second portion that defines an area other than the first portion. The heat processing part has at least one groove, which comprises a vacuum space formed on at least one edge of the reaction plate corresponding to the area of the second portion; or a first hole formed on at least one edge of the reaction plate corresponding to the area of the second portion and a second hole formed on an edge of the cover plate corresponding to the first hole to communicate with the first hole. The groove is adapted to maintain a vacuum state, and comprises a heat insulating part adapted to insulate the heat supplied to the reaction plate; or is a cooling passage adapted to allow a cooling medium to flow and comprises a cooling part adapted to cool the heat supplied to the reaction plate. The groove is formed through the bonding between the reaction plate and the cover plate. The at least one groove (preferably several grooves) is formed on several edges of the reaction plate so as to surround the entire first portion. The bonding part is fused in contact portion between the reaction plate and the cover plate to bond the reaction plate with the cover plate. A catalyst layer is formed in the channel of the at least one reaction plate. The reformer further comprises: several reaction parts formed by stacking several reaction plates adjacent to one another, each reaction plate including a channel formed in its surface; the cover plate disposed on the surface of an uppermost part of the reaction plates; the bonding part formed between the reaction plates and the uppermost of the reaction plates and the cover plate to integrally fix the reaction plate and the cover plate to each other; and the heat processing part having at least one groove formed on at least one edge of each of the reaction plates, formed in at least one of the reaction plates to control thermal energy supplied to the reaction plates. The reaction parts include: a heat source part comprising a heat-source-part reaction plate having a first catalytic layer formed in its channel in which the heat source part is adapted to generate thermal energy by an oxidation reaction of a fuel and an oxidant; a reforming reaction part comprising a reforming-reaction-part reaction plate having a second catalyst layer formed in its channel, adapted to generate a reformed gas from the fuel by a reforming reaction of the fuel using the thermal energy generated by the heat source part; and further at least one carbon monoxide reducing part comprising a carbon monoxide-reducing part reaction plate having at least the third catalytic layer formed in its channel, adapted to reduce a concentration of carbon monoxide contained in the reformed gas generated by the reforming reaction; a second bonding part formed between at least the other reaction plates to integrally fix the at least two other reaction plates to each other; and second and third heat processing parts formed in the at least two other reaction plates, respectively, to control the thermal energy supplied t the at least two other reaction plates, in which the second heat processing part comprises a vacuumed groove adapted to insulate the heat supplied to one of the at least two other reaction plates, and the third heat processing part comprises a cooling groove adapted to allow a cooling medium to flow to cool the heat supplied to another one of the at least two other reaction plates.