An ink reservoir mechanism includes a ink reservioring portion for directly reservoiring ink to be supplied to an ink jet recording head, the ink reservoiring portion having a reservoiring volume which reduces with consumption of the ink and being provided with an air-liquid separation device; a negative pressure source, having a variable inner volume, for normally applying a negative pressure to the ink reservoiring portion through the air-liquid separation device; and a connection path for connecting the negative pressure source and the ink reservoiring portion through the air-liquid separation device.