A metal air battery system includes: a battery cell module configured to generate electricity by oxidation of a metal and reduction of oxygen; a plurality of air purification modules in fluid communication with the battery cell module; a compressed air supply unit configured to supply compressed air to the plurality of air purification modules; and a buffer tank disposed between the compressed air supply unit and the plurality of air purification modules, and configured to receive compressed air from the compressed air supply unit and to supply the compressed air to the plurality of air purification modules, wherein a bottom portion of the buffer tank includes a plurality of holes, and a hole of the plurality of holes corresponds to an inlet of an air purification module in the plurality of air purification modules, and the hole is directly connected to the corresponding inlet of the air purification module.