A liquid supply device that supplies a liquid to a head that ejects the liquid to an object includes a liquid storage chamber, an air introduction port, an atmospheric release flow path where one end is in communication with the air introduction port and another end is open to the atmosphere, and an air storage chamber configured to store air and provided in a portion of the atmospheric release flow path. A liquid supply flow path that supplies the liquid from the liquid storage chamber to the head is formed in a wall defining the air storage chamber. Thus, the size of a liquid ejection system is reduced.