Hydrogen production system and hot water generation system

Hydrogen production system (2A) holds the first liquid containing water by sunlight is irradiated, part of the water contained in the first liquid is decomposed into hydrogen and oxygen, and the hydrogen generator in which at least part of which is heated in the first liquid (201), by heat exchange with the heated first liquid and the second liquid in the hydrogen generation unit (201), said first the first liquid is cooled and the first heat exchanger (207), the hydrogen generator the cooled first liquid in the first heat exchanger (207) for heating the second liquid mechanism for introducing the (201) (e.g., circulation line (204) and pump (205)) and includes a.