Provided is a method of manufacturing a grain-oriented electrical steel sheet having an excellent film adhesion can be obtained. The method of manufacturing a grain-oriented electrical steel sheet includes subjecting a steel slab to hot rolling to obtain a hot-rolled steel sheet, subjecting the hot-rolled steel sheet to cold rolling once to obtain a cold-rolled steel sheet, subjecting the cold-rolled steel sheet to pickling, subjecting the cold-rolled steel sheet to decarburization annealing, applying an annealing separator to a surface of the cold-rolled steel sheet after the decarburization annealing, and subjecting the cold-rolled steel sheet to final annealing, where in the pickling, a solution with an acid concentration of 1.0 mass % to 20 mass % and an Fe ion concentration of 2 mass % to 15 mass % is used, and in the decarburization annealing, a concentration of CO in an atmosphere gas is maintained at 6 vol % or less.