A device comprising an electrode block comprising: (a) a set of three AC application electrodes, each being bent in a V shape, are arranged on a concentric circle, symmetrically with respect to a point, the set of electrodes are configured such that their polarities are capable of being switched so that one of them is a positive electrode, another one is a negative electrode, and the other one is a ground electrode, and the set of three AC application electrodes being placed in a target fluid to be subjected to reforming; (b) a ground electrode surrounding the AC application electrodes or placed inside the AC application electrodes, c) a polarity switching circuit connected to the AC application electrodes for switching the polarities of the AC application electrodes, wherein two of the three AC application electrodes are paired and supplied with AC at a predetermined timing, while the remaining one electrode is grounded, the polarity switching circuit being configured to successively change the two electrodes to be paired, among the AC application electrodes at the predetermined timing; and (d) a constant current supply configured for keeping a current value that flows between the electrodes in fluid reforming, the constant current supply having a current detector, a current control reference voltage output section, a current control comparator and a pulse width control circuit, and which the current detector is configured to detect a current that flows between the electrodes and to generate a voltage to be input to the current control comparator, and the current control reference voltage output section is connected to a reference potential input terminal of the current control comparator and configured to provide a voltage to the current control comparator, and the current control comparator is configured to compare the voltage from the current detector and the voltage from the current control reference voltage output section and to then supply an output signal to the pulse width control circuit, and the pulse width control circuit is configured to control the current supplied from a commercial power supply according to the output signal from the current control comparator and to supply the controlled current to the AC application electrodes. (a) a set of three AC application electrodes, each being bent in a V shape, are arranged on a concentric circle, symmetrically with respect to a point, the set of electrodes are configured such that their polarities are capable of being switched so that one of them is a positive electrode, another one is a negative electrode, and the other one is a ground electrode, and the set of three AC application electrodes being placed in a target fluid to be subjected to reforming; (b) a ground electrode surrounding the AC application electrodes or placed inside the AC application electrodes, c) a polarity switching circuit connected to the AC application electrodes for switching the polarities of the AC application electrodes, wherein two of the three AC application electrodes are paired and supplied with AC at a predetermined timing, while the remaining one electrode is grounded, the polarity switching circuit being configured to successively change the two electrodes to be paired, among the AC application electrodes at the predetermined timing; and (d) a constant current supply configured for keeping a current value that flows between the electrodes in fluid reforming, the constant current supply having a current detector, a current control reference voltage output section, a current control comparator and a pulse width control circuit, and which