The present invention relates to providing a nucleic acid medicine for managing a disease or disorder related to unwanted gene expression. More specifically, the inventors of the present invention developed a technique for efficiently regulating gene expression in a cell using a relatively short oligonucleotide, by establishing a method for designing a nucleic acid medicine, comprising performing structural analysis based on sequence information of a target RNA sequence as an object for gene expression regulation, calculating the probability of existence of each structure from the obtained results of the structural analysis and the energy of each structure, and calculating the existence probability in unified fashion of an endogenous stem-loop substructure, and thereby specifying a more favorable endogenous stem-loop substructure. This technique can theoretically be applied to regulation of any gene expression, and is therefore useful for treatment or prevention of various diseases and disorders.
