A liquid supplying device comprising: a tank; and a cartridge configured to be attached to the tank in a horizontal direction, the cartridge comprising a first storage chamber configured to store liquid; the tank comprising: a second storage chamber configured to store the liquid; a liquid passage in communication with the second storage chamber, the liquid passage having a first end connected to the second storage chamber and formed with a first opening, a second end opposite to the first end and formed with a second opening open to the outside, and a first horizontal portion extending from the second opening in the horizontal direction; a gas passage in communication with the second storage chamber, the gas passage having a third end connected to the second storage chamber and formed with a third opening, a fourth end opposite to the third end and formed with a fourth opening open to the outside, and a second horizontal portion extending from the fourth opening in the horizontal direction; and an air communication portion having an air communication opening allowing the second storage chamber to communicate with the outside; wherein, in an attachment state where the cartridge is attached to the tank, the first storage chamber has a portion positioned above the liquid passage and the gas passage, and the second storage chamber is positioned below the liquid passage and the gas passage; characterised in that, in the attachment state, the first storage chamber is connected with the second storage chamber via the liquid passage and the gas passage, the first storage chamber is in communication with both the second opening and the fourth opening, thereby allowing liquid to naturally drop via the liquid passage from the first storage chamber to the second storage chamber and air having the same volume as the amount of liquid introduced into the second storage chamber to be introduced into the first storage chamber via the air communication opening and the gas flow passage. a tank; and a cartridge configured to be attached to the tank in a horizontal direction, the cartridge comprising a first storage chamber configured to store liquid; the tank comprising: a second storage chamber configured to store the liquid; a liquid passage in communication with the second storage chamber, the liquid passage having a first end connected to the second storage chamber and formed with a first opening, a second end opposite to the first end and formed with a second opening open to the outside, and a first horizontal portion extending from the second opening in the horizontal direction; a gas passage in communication with the second storage chamber, the gas passage having a third end connected to the second storage chamber and formed with a third opening, a fourth end opposite to the third end and formed with a fourth opening open to the outside, and a second horizontal portion extending from the fourth opening in the horizontal direction; and an air communication portion having an air communication opening allowing the second storage chamber to communicate with the outside; a second storage chamber configured to store the liquid; a liquid passage in communication with the second storage chamber, the liquid passage having a first end connected to the second storage chamber and formed with a first opening, a second end opposite to the first end and formed with a second opening open to the outside, and a first horizontal portion extending from the second opening in the horizontal direction; a gas passage in communication with the second storage chamber, the gas passage having a third end connected to the second storage chamber and formed with a third opening, a fourth end opposite to the third end and formed with a fourth opening open to the outside, and a second horizontal portion extending from the fourth opening in the horizontal direction; and an air communication portion having an air communication opening allowing the second storage chamber to communicate with the outside; wherein, in an attachment state where the cartridge is attached to the tank, the first storage chamber has a portion positioned above the liquid passage and the gas passage, and the second storage chamber is positioned below the liquid passage and the gas passage; characterised in that, in the attachment state, the first storage chamber is connected with the second storage chamber via the liquid passage and the gas passage, the first storage chamber is in communication with both the second opening and the fourth opening, thereby allowing liquid to naturally drop via the liquid passage from the first storage chamber to the second storage chamber and air having the same volume as the amount of liquid introduced into the second storage chamber to be introduced into the first storage chamber via the air communication opening and the gas flow passage.