Aims at providing a metal oxygen battery capable of supplying oxygen and perform charge/discharge stably. A metal oxygen battery 1 includes a positive electrode 2 to which oxygen is applied as an active substance, a negative electrode 3 to which a metal is applied as an active substance, an electrolyte layer 4 disposed between the positive electrode 2 and the negative electrode 3, and a case 5 hermetically housing the positive electrode 2, the negative electrode 3, and the electrolyte layer 4. The positive electrode 2 includes an oxygen-storing material having a catalyst function with respect to a cell reaction, and a function of, during discharge, ionizing oxygen and binding the oxygen with metal ions transferring from the negative electrode 3 through the electrolyte layer 4 to the positive electrode 2 to thereby form a metal oxide, and during charge, reducing the metal oxide and storing oxygen.