A culture vessel for holding and culturing cells, the culture vessel comprising: a cell vessel body; and a connection port (205∼212) for connecting a liquid circuit which supplies the cell and culture medium to the cell vessel body, wherein the cell vessel body has at least a pair of a first vessel and a second vessel, and a vessel lid portion, wherein the first vessel and the second vessel are vessels for accommodating a culture medium and cells or only the culture medium, respectively, part of a partition between the first vessel and the second vessel being constituted to allow movement of liquids and gases, a gap which allows mutual circulation of gases being present between an upper part of the first vessel and an upper part of the second vessel, wherein, as the connection port, to the first vessel, a first supply port for supplying the culture medium and delivering and discharging gases and a first discharge port for discharging the culture medium are connected, to the second vessel, a second supply port for supplying the culture medium and delivering and discharging the gases and a second discharge port for discharging the culture medium are connected, and wherein the first supply port and the second supply port function as a passage for always passing the culture medium in one direction for the culture vessel, wherein an opening position in the first vessel of the first supply port is located in a position higher than an opening position in the first vessel of the first discharge port, and wherein an opening position to the second vessel of the second supply port is located in a position higher than an opening position to the first vessel of the first discharge port. a cell vessel body; and a connection port (205∼212) for connecting a liquid circuit which supplies the cell and culture medium to the cell vessel body, wherein the cell vessel body has at least a pair of a first vessel and a second vessel, and a vessel lid portion, wherein the first vessel and the second vessel are vessels for accommodating a culture medium and cells or only the culture medium, respectively, part of a partition between the first vessel and the second vessel being constituted to allow movement of liquids and gases, a gap which allows mutual circulation of gases being present between an upper part of the first vessel and an upper part of the second vessel, wherein, as the connection port, to the first vessel, a first supply port for supplying the culture medium and delivering and discharging gases and a first discharge port for discharging the culture medium are connected, to the second vessel, a second supply port for supplying the culture medium and delivering and discharging the gases and a second discharge port for discharging the culture medium are connected, and wherein the first supply port and the second supply port function as a passage for always passing the culture medium in one direction for the culture vessel, wherein an opening position in the first vessel of the first supply port is located in a position higher than an opening position in the first vessel of the first discharge port, and wherein an opening position to the second vessel of the second supply port is located in a position higher than an opening position to the first vessel of the first discharge port.