It is an object to provide a blade member for an airplane which is simple in structure, and moreover is excellent with respects to weight, aerodynamic performance, cost, strength and durability. A vane of a double-slotted flap includes: an outer skin area surrounded by a first outer skin, a second outer skin, a leading edge and a trailing edge each having a predetermined wall thickness. Front and rear reinforcing areas are provided that extend in a span direction within the outer skin area and are connected to the first outer skin and the second outer skin. The outer skin area and the reinforcing areas are integrally formed by wire electrical discharge-machining. The first outer skin and the second outer skin respectively have thickened portions thicker than the other portions, and the trailing edge is formed to have a thickness which is approximately zero. This blade member can be simplified in structure, leading to reductions in the number of parts, number of assembling steps and weight. Moreover, no step nor seam is generated on a surface of the blade member, and hence it is possible to prevent an increase in drag and the generation of corrosion.