A nanometer size roughened structure is formed on a surface of a
light-emitting element, and luminous efficiency is improved.The roughened
structure on the surface of the light-emitting element of the invention
is formed into the following shape such that the refractive index
smoothly changes: (1) the mean diameter of projections on the roughened
surface is smaller than the light wavelength; (2) a pitch of the
roughened surface is irregular; and (3) positions of the top and bottom
of the roughened surface are distributed from their mean values within
the light wavelength in order to give a smooth gradient of the refractive
index. The surface of such light-emitting element is obtained by forming
a thin film on the surface of the light-emitting element using a resin
composition which contains a block copolymer or graft copolymer and forms
a micophase-separated structure in a self-organization manner;
selectively removing at least one phase of the microphase-separated
structure of the thin film formed on the surface; and etching the surface
of the light-emitting element using the remaining phase as an etching
mask.