An ink jet printer includes a recording head having nozzles for jetting ink onto a recording medium, an intermediate tank for temporarily storing ink in a lower position of the recording head, and an ink supply line for feeding the ink between the intermediate tank and the recording head, wherein when a viscosity of the ink is and pressure loss which allows the ink to be stably jetted is h, a length L and a diameter d of the ink supply line satisfy an inequality: (2.82310⁹d⁴)/L/h.