PURPOSE: To satisfactory exhibit an original function of a closely stuck sprue and to from a connecting part between a casting and the sprue part to as sharp edge by forming a boundary part and its neiborhood between a pattern for forming the casting and a pattern for forming the sprue part to the integrated pattern.

CONSTITUTION: The boundary part and its neiborhood between the pattern 9 for forming the casing and the pattern 10 for forming the sprue part are formed to the integrated pattern 13. The lower end part of the pattern 13 is fitted by drilling a spigot part 14 on a pattern base plate 8. By this method, in the boundary part of the patterns 9, 10, the sharp edge 13a is formed with the pattern 13 and even in the case of making the mold, the edge 13a is faithfully reproduced, and cutting mark from the connecting part is finely formed.