To provide a method capable of efficiently forming a structural body free from any defects or defective shape, and having a projection part of slender section.

The manufacturing method comprises a process to prepare a composite member provided with a first layer 10 of a conductive material, and a second layer 20 of a non-conductive material formed on an upper layer thereof, a process to provide a groove part 22 reaching an interface between the first layer and the second layer from the surface of the second layer of this composite member, a process to form a conductive film 30 on the surface of the second layer, a process to provide a peelable film 40 on the surface of the second layer and an inner surface of the groove part, and a process to implement the electroforming by connecting the first layer to a negative electrode of a power source, and to precipitate a metal in the groove part and on the surface of the second layer to form a projection part 80b and a body 80a of a structural body 80.