It is an object of present invention to select the most suitable composition and molding condition for obtaining a glass having a desired refractive index by press molding without any annealing treatment, for a short period of time so as to produce efficiently the glass. In the invention, a glass composition showing a target refractive index in the case where annealing is conducted is regarded as a basic composition, a component ratio of the basic composition is changed with defining as a predetermined range a range where values of the target refractive index+(100 to 850)×10−5 are upper and lower limits, a plurality of glass compositions whose estimated refractive index values estimated based on a variation in composition from the above basic composition are regularly changed within the predetermined range are provided as candidate compositions, glass molded articles having the above candidate compositions are prepared under a predetermined condition and the refractive indices thereof are measured, and the candidate composition of the glass molded article having a measured refractive index value coincident with or closest to the target refractive index is determined as an implementation composition. In the case where the measured refractive index is not coincident therewith, the molding condition is regularly changed, glass molded articles having the implementation composition are obtained under the above plurality of molding conditions and the refractive indices thereof are measured, and a molding condition of the glass molded article having a refractive index coincident with or closest to the target refractive index is determined as an implementation condition.