An optical design method attempting facilitation of optical design of a configuration including a metalens. The optical design method includes a setting step, a first calculating step, a first identifying step, a second calculating step, a second identifying step, and a designing step. The first calculating step calculates first phase data indicating a relation of a phase to a shape of a meta-atom based on a preliminarily set first wavelength. The first identifying step calculates a first phase pattern from a first step pattern and identifies a fine pattern indicating the shape of the meta-atom corresponding to the first phase pattern by referring to the first phase data. The second calculating step calculates second phase data different from the first phase data based on a preliminarily set second wavelength different from the first wavelength.