NOVELTY - Photochemical hydrogen generating device comprises multiple photoelectrode having a photoactive semiconductor layer formed on entire surface of conductive substrate, a photoelectrode module equipped with a bias power source formed on other surface of the conductive substrate, a hydrogen collecting module installed at position facing the photoactive semiconductor layer for collecting generated hydrogen and acting as counter electrode, and a reaction tank for storing electrolytic aqueous solution and is mounted with the photoelectrode module and the hydrogen collecting module.    USE - The device is useful in photochemical water decomposition device (claimed).    ADVANTAGE - The device facilitates mass production of hydrogen.    DETAILED DESCRIPTION - Photochemical hydrogen generating device comprises multiple photoelectrode having a photoactive semiconductor layer formed on the entire surface of a conductive substrate, a photoelectrode module (200) equipped with a bias power source as a bias voltage source formed on the other surface of the conductive substrate corresponding to the photoelectrode, a hydrogen collecting module (300) installed at a position facing the photoactive semiconductor layer for collecting generated hydrogen and acting as a counter electrode, and a reaction tank (100) for storing electrolytic aqueous solution and is mounted with the photoelectrode module and the hydrogen collecting module. INDEPENDENT CLAIMS are also included for:    (1) photoelectrode module for water decomposition, comprising multiple photoelectrodes provided with photoactive semiconductor layer formed on the entire surface of the conductive substrate, and the bias power source as a bias voltage source formed on the other surface of the conductive substrate corresponding to the photoelectrode; and    (2) photochemical water decomposition device comprising multiple photochemical hydrogen generating devices, a pump for supplying the electrolytic aqueous solution to the hydrogen generating device, and a collecting duct for collecting hydrogen gas generated in the hydrogen generating device.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the photochemical water decomposition hydrogen generating device.    Reaction tank (100)    Photoelectrode module (200)    Hydrogen collecting module (300)    Discharging tube (310)    Branching tube (320)