A galvannealed steel sheet includes: a steel sheet; a galvannealed layer which is formed on at least one surface of the steel sheet and includes Al, Fe, and the balance composed of Zn and inevitable impurities; and a composite oxide layer of Mn, Zn, and P which is formed on the surface of the galvannealed layer, includes Mn, P, and Zn, and has the P/Mn ratio of equal to or higher than 0.3 and equal to or lower than 50. The galvannealed layer includes a flat portion having an area ratio of equal to or higher than 10% and equal to or lower than 70% and a rough portion which is at a position closer to the steel sheet than the flat portion at the interface of the galvannealed layer and the composite oxide layer 5. The composite oxide layer of Mn, Zn, and P contains an amorphous compound.