An opening and closing unit for opening and closing an ink flow passage and a filter chamber in which a filter is arranged horizontally are provided in an ink supply system. The opening and closing unit is disposed upstream of the filter chamber, a first room is disposed downstream of the filter and a second room is upstream of the filter in the filter chamber. An ink discharge opening is disposed in the first room, and an ink supply opening and an air bubble storage unit for storing the air bubble flowing in with the ink are disposed in the second room. The ink supply opening and the ink discharge opening are displaced with respect to each other in a horizontal direction for arrangement. The air bubble storage unit is arranged upward of the ink supply opening in a perpendicular direction. A suction unit expands the air bubble stored in the air bubble storage unit.