The invention describes a method of manufacturing a holographic mask capable of producing an image pattern that contains elements of a subwavelength size along with decreased deviations from the original pattern. The original pattern is converted into a virtual electromagnetic field and is divided into a set of virtual cells with certain amplitudes and phases, which are mathematically processed for obtaining the virtual digital hologram. In the calculation of virtual components of the hologram, the method includes a step, wherein as a result of the preliminary divergence of the initial light beam, the entire virtual hologram is increased in proportion to the degree of the divergence of the initial light beam. This facilitate virtual processing of the fine and delicate elements of the virtual hologram. Upon completion of the virtual processing, the final data needed for manufacturing of the actual digital hologram, e.g., on a lithograph, are obtained.