To solve a problem that a great deal of time and labor is required and manufacturing costs, and casting costs as well increase if an individual model is manufactured separately for every product in manufacturing the models.

A model apparatus for a mold is provided with a plurality of model members formed by dividing a basic model, and auxiliary model members having notches which are nearly formed into the shape of the model members and can be engaged with the model members. Therefore, models with nearly the same shape and different dimensions can be manufactured by varying the size of the auxiliary model members. As it is not necessary to manufacture an individual model separately for every product, unlike before, in manufacturing models with nearly the same shape and different dimensions, neither much time nor much labor is required, and manufacturing costs and casting costs as well can be prevented from rising. As a result, the efficiency of the casting work can be enhanced regarding each product with nearly the same shape and different dimensions.