NOVELTY - A photosynthetic reactor comprising a photosynthetic microorganism layer (PML) (2) and a culture solution layer (CSL) (1), separated by a transparent permeable film (3), is new.    USE - The reactor is useful for photosynthesis of useful substances such as hydrogen and biodegradable plastics from organic waste, carbon dioxide and/or water. It is also useful for environmental purification and for fixing carbon dioxide, therefore preventing global warming.    ADVANTAGE - The light reflecting surfaces in PML and CSL of the reactor efficiently diffuses light to the middle and lower parts of the reactor, enabling a stable and continuous photosynthesis reaction and culture of microbes, and minimizing leakage of light from the reactor. Since the membrane is not permeable to microbes, their movement is restricted and need for fixing the microorganisms is eliminated. Since the microorganisms are not fixed on the reactor, denaturation or deactivation of microorganism is prevented and maintenance of PML at optimum stage, effectively stabilizes the culture for a long period. The reactor is compact as usage of beam condensing unit and light diffusion units are eliminated. Hence installation cost of the reactor is reduced. The reactor effectively enables environmental purification and fixes carbon dioxide preventing global warming.    DETAILED DESCRIPTION - A photosynthetic reactor comprises photosynthetic microorganism layer (PML) (2) and culture solution layer (CSL) (1), separated by a transparent permeable film (3). Both the layers are provided with light receiving surfaces. On light irradiation, the microorganism performs photosynthesis of hydrogen and bio-degradable plastics from organic wastes and carbon dioxide, and the culture solution layer enables culture of a photosynthetic microorganism. Two or more CSL and PML are arranged alternately in the reactor.    DESCRIPTION OF DRAWING(S) - The figure shows the perspective diagram of a photosynthetic reactor. The drawing contains non-English language text.    Culture solution layer (1)    Photosynthetic microorganism layer (2)    Transparent permeable film (3)    Culture solution inlet (4)    Drainage outlet (5)    Light receiving surface (7)