A lithium ion oxygen battery capable of achieving a high energy density without being decreased in performance due to moisture or carbon dioxide in the atmosphere is provided. A lithium ion oxygen battery 1 comprises a positive electrode 2 containing oxygen as an active material and a lithium source, a negative electrode 3 made of a material capable of occluding or releasing lithium ions, and an electrolyte layer 4 sandwiched between the positive electrode 2 and the negative electrode 3 and capable of conducting the lithium ions. The positive electrode 2, the negative electrode 3, and the electrolyte layer 4 are housed in a hermetic case 5. The positive electrode 2 comprises an oxygen storage material and a lithium compound (excluding a combined metal oxide of lithium and another metal) as the lithium source.