An air battery system has a sealed air battery cell (10) having: an air electrode having an air electrode layer (4) containing a conductive material and an air electrode power collector (6) for collecting electric power from the air electrode layer; a negative electrode having a negative electrode layer (3) containing an negative electrode active material that adsorbs and releases metal ions and a negative electrode power collector (2) for collecting electric power from the negative electrode layer; a separator (7) provided between the air electrode layer and the negative electrode layer; and a sealed air battery case (1a, 1b). The air battery system also has a depressurization portion (20) that reduces the internal pressure of the sealed air battery cell to below the atmospheric pressure.