A geological storage system of carbon dioxide according to an exemplary embodiment of the present invention includes: an injection pipe that extends to a carbon storage reservoir that includes a plurality of rock grains and brine, from the ground surface, and supplies an injection material that includes carbon dioxide (CO2) to the carbon storage reservoir; a plurality of pores that are disposed between the plurality of rock grains; and a storage structure that is connected with a part of the plurality of pores and where the carbon dioxide reaches through the plurality of pores and then stored.