To provide an air electrode material powder for a solid oxide fuel cell, comprising a novel LSCF powder having a highly uniform composition suitable as an air electrode material for a solid oxide fuel cell, and its production process.A composite oxide having a perovskite structure and containing lanthanum, strontium, cobalt, iron and oxide, wherein the dispersion point determined by the peak intensity [La] of the Lα1 characteristic X-ray of lanthanum and the peak intensity [Sr] of the Lα1 characteristic X-ray of strontium as obtained by EPMA measurement, is present within a range of the formula (1) and the dispersion point determined by the peak intensity [Co] of the Kα1 characteristic X-ray of cobalt and the peak intensity [Fe] of the Kα1 characteristic X-ray of iron is present within a range of the formula (2): a[La]−150≦[Sr]≦a[La]+150  (1) b[Co]−300≦[Fe]≦b[Co]+300  (2) wherein 0.2≦a≦1.0 and 0.1≦b≦4.0.