Abstract: This injection molding method includes the steps of: constructing a prediction model on the basis of an input parameter including a molding condition for a molding product and an objective variable value including a quality value that quantifies a required quality of the molding product with respect to the input parameter; inferring a predictive distribution of the objective variable value with respect to the input parameter, using the prediction model; and deriving such a molding condition that satisfies the required quality of the molding product, by a Bayesian optimization method utilizing a regression model for obtaining the input parameter that yields a quality value highest in evaluation of the objective variable value as compared to an initial quality value, on the basis of the predictive distribution.