To provide a liquid feeder equipped with a nonreturn mechanism of a simple structure which passes a gas within a liquid storage means and prevents invasion of the gas from the outside to the liquid storage means, and to provide a liquid ejecting apparatus equipped with the liquid feeder.

An atmosphere communication hole 104 is formed in a sub tank 101. At the same time, a gas permeation film 105 which separates the inside of a tank body 102 and the atmosphere side from each other is set in the atmosphere communication hole 104. An oil 106 is filled in the atmosphere side of the atmosphere communication hole 104 separated by the gas permeation film. A diametrical size of an upper communication hole 104c of the atmosphere communication hole 104 is made smaller than that of a middle communication hole 104b. Even when the sub tank 101 is reversed in an upside-down direction, a pressure loss without accompanying a leak of the oil 106 is generated by the diametrical size. Thus the air within the sub tank is discharged to the atmosphere through the gas permeation film 105 and the oil 106 when the sub tank is pressured. When the sub tank interior becomes a negative pressure, a back flow of the air is prevented by the oil 106.