A three-dimensional nanostructures and a method for fabricating the same, and more particularly to three-dimensional structures of various shapes having high aspect ratio and uniformity in large area and a method of fabricating the same by attaching a target material to the outer surface of patterned polymer structures using an ion bombardment phenomenon occurring during a physical ion etching process to form target material-polymer composite structures, and then removing the polymer from the target material-polymer structures. A three-dimensional nanostructures with high aspect ratio and uniformity can be fabricated by a simple process at low cost by using the ion bombardment phenomenon occurring during physical ion etching. Also, nanostructures of various shapes can be easily fabricated by controlling the pattern and shape of polymer structures. In addition, uniform fine nanostructures having a thickness of 10 nm or less can be formed in a large area.