A method for manufacturing a wound magnetic core, comprising: - a first operation in which a non-magnetic insulating metal oxide powder is made to adhere to a surface of a soft magnetic metal ribbon (10, 100) having an amorphous structure; - a second operation in which, following the first operation, the soft magnetic metal ribbon (10, 100) is wound in annular fashion to obtain a wound body at which the metal oxide powder and air layers intervenes between layers of the ribbon; - a third operation in which the wound body is made to undergo heat treatment in a non-oxidizing atmosphere; - a fourth operation in which, following the third operation, the wound body is subjected to treatment for formation of an oxide film by supplying oxygen to the outer surface of the wound body and the air layers inside of the wound body in an oxidizing atmosphere at a temperature lower than a heat treatment temperature at the third operation to cause oxidation of the surface of the soft magnetic metal ribbon (10, 100) in contact with the outer surface and the air layers inside the wound body; and - a fifth operation in which, following the fourth operation, spaces between the layers of the ribbon of the wound body are impregnated with resin and curing thereof is carried out; wherein the treatment for formation of the oxide film at the fourth operation is carried out at a temperature that is not less than 240 °C but less than the heat treatment temperature at the third operation, wherein an amount of the metal oxide powder which is made to adhere thereto at the first operation is not less than 0.1 % but not greater than 1.2 % when expressed as a metal oxide powder wt.% ratio as obtained using the following Formula; and metal oxide wt.% ratio (%) = (weight of metal oxide adhering to soft magnetic metal ribbon (10, 100) / weight of soft magnetic metal ribbon (10, 100)) x 100 wherein an average particle diameter, median diameter of a cumulative particle size distribution, of the metal oxide powder is not less than 0.5 μm but not greater than 1.0 μm. - a first operation in which a non-magnetic insulating metal oxide powder is made to adhere to a surface of a soft magnetic metal ribbon (10, 100) having an amorphous structure; - a second operation in which, following the first operation, the soft magnetic metal ribbon (10, 100) is wound in annular fashion to obtain a wound body at which the metal oxide powder and air layers intervenes between layers of the ribbon; - a third operation in which the wound body is made to undergo heat treatment in a non-oxidizing atmosphere; - a fourth operation in which, following the third operation, the wound body is subjected to treatment for formation of an oxide film by supplying oxygen to the outer surface of the wound body and the air layers inside of the wound body in an oxidizing atmosphere at a temperature lower than a heat treatment temperature at the third operation to cause oxidation of the surface of the soft magnetic metal ribbon (10, 100) in contact with the outer surface and the air layers inside the wound body; and - a fifth operation in which, following the fourth operation, spaces between the layers of the ribbon of the wound body are impregnated with resin and curing thereof is carried out; the treatment for formation of the oxide film at the fourth operation is carried out at a temperature that is not less than 240 °C but less than the heat treatment temperature at the third operation, wherein an amount of the metal oxide powder which is made to adhere thereto at the first operation is not less than 0.1 % but not greater than 1.2 % when expressed as a metal oxide powder wt.% ratio as obtained using the following Formula; and metal oxide wt.% ratio (%) = (weight of metal oxide adhering to soft magnetic metal ribbon (10, 100) / weight of soft magnetic metal ribbon (10, 100)) x 100 wherein an average particle diameter, median diameter of a cumulative particle size distribution, of the metal oxide powder is not less than 0.5 μm but not greater than 1.0 μm.