A supply liquid tank unit of the present disclosure includes a supply liquid tank and a detection sensor. The detection sensor detects a liquid surface of ink in the supply liquid tank. The supply liquid tank is provided with an inner space having a storage chamber which stores the ink and an atmosphere release port for making an inner pressure in the inner space equal to an atmospheric pressure. The detection sensor has a float which moves vertically in accordance with an amount of the ink in the storage chamber and a sensor main body which detects a liquid surface of the ink when the float moves vertically. An inner side surface of the storage chamber is disposed along and near an outer circumferential surface of the float.