NOVELTY - A hydrogen generation system (100) comprises 1st electrode containing photocatalytic semiconductor, 2nd electrode electrically connected with 1st electrode, water-containing electrolyte solution which contacts surface of 1st and 2nd electrodes and is positioned between 1st and 2nd electrodes, separator which divides electrolyte solution into 1st electrolyte which contacts surface of 1st electrode and 2nd electrolyte solution which contacts surface of 2nd electrode, and housing which accommodates 1st electrode, 2nd electrode, electrolyte solution, and separator.    USE - A hydrogen generation system for electric power generation system for household use and business use.    ADVANTAGE - Heat is efficiently recovered without reducing hydrogen generation efficiency, and diffusion of ion in electrolyte solution is not prevented.    DETAILED DESCRIPTION - A hydrogen generation system (100) comprises 1st electrode containing photocatalytic semiconductor, 2nd electrode electrically connected with 1st electrode, water-containing electrolyte solution which contacts surface of 1st and 2nd electrodes and is positioned between 1st and 2nd electrodes, separator which divides electrolyte solution into 1st electrolyte which contacts surface of 1st electrode and 2nd electrolyte solution which contacts surface of 2nd electrode, and housing which accommodates 1st electrode, 2nd electrode, electrolyte solution, and separator. Hydrogen generation device decomposes water and produces hydrogen by irradiating light to photocatalytic semiconductor of 1st electrode. The mechanism in which 1st electrolyte solution is circulated using 1st circulation path (201) which leads 1st electrolyte solution out of hydrogen generation device and introduces again in hydrogen generation device, wherein 1st circulation path contains 1st heat exchanger (204) and temperature measurement apparatus (203) for measuring temperature of 1st electrolyte solution. When temperature of measured 1st electrolyte solution is more than predetermined temperature, heat exchange with 1st electrolyte solution of 1st circulation path and 1st liquid of 1st fluidic diagram (205) is performed, 1st electrolyte solution is cooled, and 1st liquid is heated.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a hydrogen generation system. (Drawing includes non-English language text).    Hydrogen generation system (100)    1st circulation path (201)    1st temperature measurement apparatus (203)    1st heat exchanger (204)    1st fluidic diagram (205)