A liquid supply unit includes a first chamber communicating with a liquid storage container, a second chamber communicating with a liquid ejection head, a communication opening allowing communication between the both chambers, an opening/closing member configured to open and close the communication opening, a biasing member configured to bias the opening/closing member in a direction toward the closing posture, a pressing member capable of pressing the opening/closing member in a direction toward the opening posture, and a flexible film member configured to be displaced based on a negative pressure. The pressing member includes a pivot portion, a pressure receiving portion configured to receive the displacement force from the flexible film member and a pressing portion configured to press the opening/closing member. The pivot portion is arranged on one end side of the pressing member, and the pressing portion is arranged on the other end side of the pressing member.