A CAE analysis die model is produced such that a cavity of a die for obtaining a cast product is divided into multiple elements. Fluidity analysis and solidification analysis are performed under a predetermined casting condition by means of the die model to calculate, for each element, a factor regarding growth of a solidification structure, a factor regarding purity of molten metal, and a factor regarding a hole defect. Mechanical characteristics of each portion of the cast product are obtained by a regression expression obtained by multiple regression analysis using mechanical characteristics of the cast product as an objective variable and using each factor as an explanatory variable.