A liquid supplying device includes a tank and a cartridge. The cartridge is configured to be detachably attached to the tank in an attachment-detachment direction crossing a vertical direction. The cartridge includes a first storage chamber. The tank includes a second storage chamber, a liquid passage, and a gas passage. The liquid passage has a first end, a second end, and a first extending portion. The second end is formed with a second opening open to an atmosphere. The first extending portion extends from the second opening in the attachment-detachment direction. The gas passage has a third end, a fourth end, and a second extending portion. The fourth end is formed with a fourth opening open to the atmosphere. The second extending portion extends from the fourth opening in the attachment-detachment direction. The second opening is at a position different from the fourth opening in the attachment-detachment direction.