A nickel-hydrogen secondary battery includes an electrode group including a separator, a positive electrode and a negative electrode, the positive electrode includes a positive electrode active material, the positive electrode active material includes a composite particle including a compound of Co and a compound of Ni, and the ratio R represented by A/B satisfies a relationship of R≥0.3, when the amount of jumping in the X-ray absorption fine structure spectrum of the Co in 7600 to 7800 eV and the amount of jumping in the X-ray absorption fine structure spectrum of the Ni in 8300 to 8500 eV obtained by measurement according to a conversion electron yield method are defined as A and B, respectively.