A tank unit comprising: a first bottom wall spreading in a first direction and a second direction, the first direction being along a horizontal plane, the second direction being along the horizontal plane and crossing the first direction; a second bottom wall spreading in the first direction and the second direction, the second bottom wall defining an opening (OP1, OP2) penetrating therethrough in a vertical direction; a first side wall spreading in the vertical direction and the second direction, the first side wall having an upper end part and a lower end part, the upper end part being connected to an end part on one side in the first direction of the second bottom wall, the lower end part being connected to an end part on the other side in the first direction of the first bottom wall; characterized in that: the second bottom wall is positioned above the first bottom wall; and the tank unit further comprises: a tank arranged on an upper surface of the first bottom wall and which is configured to store ink; a liquid level sensor configured to detect a liquid level of the ink inside the tank; a substrate electrically connected to the liquid level sensor; a first internal wiring having one end connected to the substrate; a first internal tube which has one end connected to the tank and through which the ink to be supplied to the tank flows; a first electric interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal wiring is connected; and a first fluidic interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal tube is connected. a first bottom wall spreading in a first direction and a second direction, the first direction being along a horizontal plane, the second direction being along the horizontal plane and crossing the first direction; a second bottom wall spreading in the first direction and the second direction, the second bottom wall defining an opening (OP1, OP2) penetrating therethrough in a vertical direction; a first side wall spreading in the vertical direction and the second direction, the first side wall having an upper end part and a lower end part, the upper end part being connected to an end part on one side in the first direction of the second bottom wall, the lower end part being connected to an end part on the other side in the first direction of the first bottom wall; characterized in that: the second bottom wall is positioned above the first bottom wall; and the tank unit further comprises: a tank arranged on an upper surface of the first bottom wall and which is configured to store ink; a liquid level sensor configured to detect a liquid level of the ink inside the tank; a substrate electrically connected to the liquid level sensor; a first internal wiring having one end connected to the substrate; a first internal tube which has one end connected to the tank and through which the ink to be supplied to the tank flows; a first electric interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal wiring is connected; and a first fluidic interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal tube is connected. the second bottom wall is positioned above the first bottom wall; and the tank unit further comprises: a tank arranged on an upper surface of the first bottom wall and which is configured to store ink; a liquid level sensor configured to detect a liquid level of the ink inside the tank; a substrate electrically connected to the liquid level sensor; a first internal wiring having one end connected to the substrate; a first internal tube which has one end connected to the tank and through which the ink to be supplied to the tank flows; a first electric interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal wiring is connected; and a first fluidic interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal tube is connected. a tank arranged on an upper surface of the first bottom wall and which is configured to store ink; a liquid level sensor configured to detect a liquid level of the ink inside the tank; a substrate electrically connected to the liquid level sensor; a first internal wiring having one end connected to the substrate; a first internal tube which has one end connected to the tank and through which the ink to be supplied to the tank flows; a first electric interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal wiring is connected; and a first fluidic interface which is positioned inside the opening of the second bottom wall and to which the other end of the first internal tube is connected.