The backing pressure of an ink tank is controlled. The ink tank is connected to a pressure control apparatus. The pressure control apparatus has first and second check valves. When the internal pressure of the ink tank becomes smaller than that of outside atmosphere by a first predetermined pressure or more, the first check valve is switched into an open state to connect the outside atmosphere and the ink tank. To the contrary, when the internal pressure of the ink tank becomes larger than that of outside atmosphere by a second predetermined pressure or more, the second check valve is switched to an open state to connect the ink tank with the outside atmosphere. Therefore, the internal pressure of the ink tank is controlled precisely enough to stabilize the meniscus.