PURPOSE: To feed in a product having optimal quality by calculating and determining each use ratio of plural raw materials by considering plural component values decided to exert influence on the quality of a formed product obtained from a blending raw material.

CONSTITUTION: In step 1, a use raw material is selected as an input variable from raw materials of plural brands, and a temporary use ratio is set. In step 2, by fractionalizing the input variable and setting two groups to be increased as one set, all combinations are organized. In step 3, at every organization unit, each component value is calculated according to the temporary use ratio. In step 4, a target component value provided with the upper and the lower limit constraint values is set, and in step 5, each component value of each organization unit and the target component value are compared, the organization units of which the vector direction coincide with each other are searched, and one organization unit of the vector, whose number of coincidences with the component of high priority is large, is selected. In step 6, by the selected organization unit, a use ratio of a brand, in which the component value of high priority is near a target, and also, there is no deviation of the upper and the lower constraint values in other component is calculated.