A galvannealed steel sheet comprising: a steel sheet; a galvannealed layer which is formed on at least one surface of the steel sheet and includes an amount equal to or more than 0.05 mass% and equal to or less than 0.5 mass% of Al, an amount equal to or more than 6 mass% and equal to or less than 12 mass% of Fe, and optionally an amount equal to or less than 2 mass% of at least one of Pb, Sb, Si, Sn, Mg, Mn, Ni, Cr, Co, Ca, Cu, Li, Ti, Be, Bi, and rare earth elements, and the balance composed of Zn and inevitable impurities; wherein the steel sheet upon which the galvannealed layer is formed is subjected to skin pass rolling at an elongation ratio of equal to or more than 0.3%; and a mixed layer which is formed on a surface of the galvannealed layer using a roll coater having protrusions and recesses and includes a composite oxide of Mn, Zn, and P and an aqueous P compound that contains at least one kind of PO 4 3-, PO 3 2-, and PO 2 -, wherein the composite oxide includes an amount equal to or more than 0.1 mg/m 2 and equal to or less than 100 mg/m 2 of Mn, an amount equal to or more than 1 mg/m 2 and equal to or less than 100 mg/m 2 of P, and Zn, and has a P/Mn ratio of equal to or higher than 0.3 and equal to or lower than 50, wherein the composite oxide of Mn, Zn, and P mainly contains an amorphous compound, wherein the mixed layer includes a first applied part as formed using the protrusions of the roll coater and a second applied part as formed using the recesses of the roll coater, an attached amount of P in the second applied part being larger than an attached amount of P in the first applied part, the attached amount of P in the second applied part being equal to or more than 20 mg/m 2, and wherein a total surface area of the second applied part, measured according to the method mentioned in the description of the application as filed, is equal to or higher than 20% and equal to or lower than 80% of a surface area of the mixed layer. a steel sheet; a galvannealed layer which is formed on at least one surface of the steel sheet and includes an amount equal to or more than 0.05 mass% and equal to or less than 0.5 mass% of Al, an amount equal to or more than 6 mass% and equal to or less than 12 mass% of Fe, and optionally an amount equal to or less than 2 mass% of at least one of Pb, Sb, Si, Sn, Mg, Mn, Ni, Cr, Co, Ca, Cu, Li, Ti, Be, Bi, and rare earth elements, and the balance composed of Zn and inevitable impurities; wherein the steel sheet upon which the galvannealed layer is formed is subjected to skin pass rolling at an elongation ratio of equal to or more than 0.3%; and a mixed layer which is formed on a surface of the galvannealed layer using a roll coater having protrusions and recesses and includes a composite oxide of Mn, Zn, and P and an aqueous P compound that contains at least one kind of PO 4 3-, PO 3 2-, and PO 2 -, wherein the composite oxide includes an amount equal to or more than 0.1 mg/m 2 and equal to or less than 100 mg/m 2 of Mn, an amount equal to or more than 1 mg/m 2 and equal to or less than 100 mg/m 2 of P, and Zn, and has a P/Mn ratio of equal to or higher than 0.3 and equal to or lower than 50, wherein the composite oxide of Mn, Zn, and P mainly contains an amorphous compound, wherein the mixed layer includes a first applied part as formed using the protrusions of the roll coater and a second applied part as formed using the recesses of the roll coater, an attached amount of P in the second applied part being larger than an attached amount of P in the first applied part, the attached amount of P in the second applied part being equal to or more than 20 mg/m 2, and wherein a total surface area of the second applied part, measured according to the method mentioned in the description of the application as filed, is equal to or higher than 20% and equal to or lower than 80% of a surface area of the mixed layer.