To provide an apparatus for culturing algae, capable of feeding sufficient carbon dioxide to a culture liquid of the algae, inhibiting the decrease of a pH value, and enabling the algae to be readily and efficiently cultured at a low cost.

The apparatus for culturing the algae includes a sealed culture vessel into which the culture liquid for culturing the algae can be inserted, and a ventilation means for injecting the carbon dioxide gas to the vapor phase in the sealed culture vessel and automatically discharging the pressure over a prescribed value to culture the algae in a common anaerobic atmosphere.