PROBLEM TO BE SOLVED: To provide a separation system of photosynthetic microorganisms and a separation method of the photosynthetic microorganisms, which can precipitate photosynthetic microorganisms sufficiently to separate them from a culture medium.SOLUTION: A separation system of photosynthetic microorganisms precipitates the photosynthetic microorganisms contained in a culture medium containing the photosynthetic microorganisms, in the culture medium, to separate the photosynthetic microorganisms from the culture medium. The separation system includes a dissolved oxygen reduction tub 1 provided with dissolved oxygen reduction devices (aeration pipe 3 and blower 8) which reduce a dissolved oxygen concentration of the culture medium. The separation system 10 and a separation method of the photosynthetic microorganisms are provided.
