An exhaust valve apparatus and a drier of a food treatment system having the exhaust valve apparatus are disclosed. The drier includes a drum having an input port and a discharge port. A stirring screw is rotatably disposed in the drum, and includes rotary blades for stirring and crushing the food waste and a rotating shaft for supporting the rotary blades. A power supply unit is provided on a surface of the drum and provides power to the stirring screw to rotate the stirring screw. A heater is provided on the outer surface of the drum body and provides high temperature heat to the inner space of the drum when electric power is applied to the heater, thus drying the food waste. An exhaust apparatus is mounted to the lower surface of the discharge port to open or close the discharge port.