A fluid circulation apparatus, comprising: a first tank to store fluid to be supplied to a fluid ejection head ; a circulation path including a first flow path portion to provide fluid from the first tank to a supply port of the fluid ejection head, and a second flow path portion to return fluid from a collection port of the fluid ejection head to the first tank ; a bypass flow path to connect the supply port to the collection port outside of the fluid ejection head , allowing the fluid to flow from the supply port to the collection port ; characterized in that the apparatus comprises: a bypass tank in the bypass flow path , comprising an air chamber and a lower region formed by the fluid flowing through the bypass tank ; a pressure sensor measuring the pressure of the bypass flow in the air chamber of the bypass tank ; an opening/closing valve connected to an air chamber of the bypass tank and configured to selectively open the air chamber to the atmosphere; a circulation pump in the circulation path between the first tank and the fluid ejection head, the circulation pump being configured to send the fluid from the first tank toward the fluid ejection head; and a processor configured to adjust fluid output rates of the circulation pump based on pressure of the air chamber of the bypass tank as detected by the pressure sensor; wherein the pressure sensor detects pressure of the air chamber of the bypass tank. a first tank to store fluid to be supplied to a fluid ejection head ; a circulation path including a first flow path portion to provide fluid from the first tank to a supply port of the fluid ejection head, and a second flow path portion to return fluid from a collection port of the fluid ejection head to the first tank ; a bypass flow path to connect the supply port to the collection port outside of the fluid ejection head , allowing the fluid to flow from the supply port to the collection port ; characterized in that the apparatus comprises: a bypass tank in the bypass flow path , comprising an air chamber and a lower region formed by the fluid flowing through the bypass tank ; a pressure sensor measuring the pressure of the bypass flow in the air chamber of the bypass tank ; an opening/closing valve connected to an air chamber of the bypass tank and configured to selectively open the air chamber to the atmosphere; a circulation pump in the circulation path between the first tank and the fluid ejection head, the circulation pump being configured to send the fluid from the first tank toward the fluid ejection head; and a processor configured to adjust fluid output rates of the circulation pump based on pressure of the air chamber of the bypass tank as detected by the pressure sensor; wherein the pressure sensor detects pressure of the air chamber of the bypass tank. a bypass tank in the bypass flow path , comprising an air chamber and a lower region formed by the fluid flowing through the bypass tank ; a pressure sensor measuring the pressure of the bypass flow in the air chamber of the bypass tank ; an opening/closing valve connected to an air chamber of the bypass tank and configured to selectively open the air chamber to the atmosphere; a circulation pump in the circulation path between the first tank and the fluid ejection head, the circulation pump being configured to send the fluid from the first tank toward the fluid ejection head; and a processor configured to adjust fluid output rates of the circulation pump based on pressure of the air chamber of the bypass tank as detected by the pressure sensor; wherein the pressure sensor detects pressure of the air chamber of the bypass tank. <EOS>