A black composite oxide particle includes a composite oxide having Fe, Mg and Al as metal components. The particle contains Fe, Mg and Al in amounts of 30 to 55 mass %, 1 to 10 mass %, and 1 to 10 mass %, respectively, and has an atomic ratio of Fe.sup.3+/Fe.sup.2+ of 0.8 to 10. Also described is a method for producing the black composite oxide particle. In an embodiment, the particle includes a hydrated composite oxide represented by an empirical formula: Fe.sup.2+.sub.aFe.sup.3+.sub.bMg.sub.cAl.sub.dO.sub.enH.sub.2O. The black composite oxide particle is suitable as a black pigment for a coating material, an ink, toner particles, a rubber and a plastic, and is reduced with respect to the load on the environment and excellent in blackness.