Abstract: A micro structure which is preferred as an original plate of an antireflection, a mold of nano imprint or injection molding is obtained by a single particle film etching mask on which each particle is precisely aligned and closest packed in two dimensions. A single particle film etching mask is produced by a drip step wherein a dispersed liquid in which particles dispersed in a solvent are dripped onto a liquid surface of a water tank, a single particle film formation step in which a single particle film which consists of the particles by volatizing a solvent is formed, and a transfer step in which the single particle film is transferred to a substrate. The single particle film etching mask on which particles are closest packed in two dimensions, has a misalignment D(%) of an array of the particles that is defined by D(%)=|B?A|×100/A being less than or equal to 10%. However, A is the average diameter of the particles, and B is the average pitch between the particles in the single particle film.