An ink supplying mechanism includes a circulating system that connects an ink jet head having a nozzle, a pressure chamber opposed to the nozzle, and an upstream port and a downstream port that communicate with the pressure chamber, an upstream side tank that communicates with the ink jet head via the upstream port and is capable of storing an ink, a downstream side tank that communicates with the ink jet head via the downstream port and is capable of storing the ink, and a circulating pump that feeds the ink from the downstream side tank back to the upstream side tank. The ink supplying mechanism has a relief valve that is capable of opening and closing at least a liquid surface of the downstream side tank with respect to the atmospheric pressure, closes the relief valve to drive the circulating pump, sets the liquid surface of the downstream side tank to a negative pressure, and feeds the ink from the downstream side tank back to the upstream side tank via a feedback channel to circulate the ink.