A galvannealed steel sheet includes: a steel sheet; a galvannealed layer; and a Mn—P based oxide film. A Zn—Fe alloy phase in the galvannealed layer is measured by X-ray diffractometry. The value of a diffraction intensity Γ(2.59 Å) of Γ phase divided by a diffraction intensity δ1(2.13 Å) of δ1 phase is less than or equal to 0.1. The value of a diffraction intensity ζ(1.26 Å) of ζ phase divided by a diffraction intensity δ1(2.13 Å) of δ1 phase is greater than or equal to 0.1 and less than or equal to 0.4. The Mn—P based oxide film is formed using 5 to 100 mg/m2 of Mn and 3 to 500 mg/m2 of P on a surface of the galvannealed layer.