Organism Culturing System and Organism Culturing Method

A system for culturing a photosynthetic organism such as a microalga has a liquid storage vessel for storing a liquid that absorbs more light in a short-wavelength range than light in a long-wavelength range, a culture vessel for storing a culture solution containing a photosynthetic organism to be cultured and disposed in the liquid storage vessel, a light quantity measuring unit for measuring the quantity of light that the culture vessel receives and a liquid depth controlling unit for controlling the liquid depth from the surface of the light-absorbing solution to the culture vessel based on the measurement result of the light quantity measuring unit. The light quantity measuring unit measures quantities of light which the culture vessel receives separately for different wavelength ranges. As a result, during the cultivation of a photosynthetic organism for the purpose of producing a biofuel or a useful substance, the increase in temperature and the defect caused by light under a strong light condition can be avoided and the decrease in photosynthetic efficiency can be made smaller.