A forming member for antireflection structure according to the present invention comprises a transfer material and a to-be-transferred material, wherein: the transfer material can be peeled off from the to-be-transferred material; the transfer material is constructed such that a structure having a reversal shape of an antireflection structure in which structural units are arranged in a shape of an array at a period smaller than a minimum wavelength of light whose reflection should be prevented and which has an aspect ratio of unity or greater is formed on a principal surface of a base substrate part having flexibility; the to-be-transferred material is a structure formed from a resin and having the same shape as the antireflection structure; and the transfer material and the to-be-transferred material are arranged such that the structure having the same shape as the antireflection structure fills up the structure having a reversal shape of the antireflection structure. Thus, even in the inside of an assembled optical apparatus, an antireflection structure can easily be formed at a predetermined position. Further, the optical characteristics of the optical apparatus itself is not affected.