NOVELTY - A gas production apparatus (800) comprises 1st electrode (310), 1st chamber formation part (110) which forms 1st chamber (210) for accommodating electrolyte solution and 1st electrode, 2nd electrode (320), 2nd chamber formation part (140) which forms 2nd chamber (220) for accommodating electrolyte solution and 2nd electrode, electroconductive part (326) containing contact part which is in contact with photocatalyst, transparent substrate provided with inner surface which is surface where 2nd electrode is fixed and is surface positioned inside the 2nd chamber, and retaining wall (130).    USE - A gas production apparatus for producing hydrogen gas and oxygen gas (claimed).    ADVANTAGE - The possibility of malfunction in case of using transparent substrate comprising electrode containing photocatalyst is reduced.    DETAILED DESCRIPTION - A gas production apparatus (800) comprises 1st electrode (310), 1st chamber formation part (110) which forms 1st chamber (210) for accommodating electrolyte solution and 1st electrode, 2nd electrode (320), 2nd chamber formation part (140) which forms 2nd chamber (220) for accommodating electrolyte solution and 2nd electrode, electroconductive part (326) containing contact part which is in contact with photocatalyst, transparent substrate provided with inner surface which is surface where 2nd electrode is fixed and is surface positioned inside the 2nd chamber, and retaining wall (130) which supports transparent substrate by enclosing edge of transparent substrate and separates inner side and exterior of 2nd chamber. The gas production apparatus generates hydrogen gas and oxygen gas using photocatalyst from electrolyte solution containing water.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional diagram of the gas production apparatus.    1st chamber formation part (110)    Retaining wall (130)    2nd chamber formation part (140)    1st chamber (210)    2nd chamber (220)    1st electrode (310)    2nd electrode (320)    Electroconductive part (326)    Gas production apparatus (800)