Conventionally a method that uses a die for casting is used to manufacture the parts of an engine of an automobile such as a cylinder head or manifold, etc., from a non-ferrous metal such as aluminum, etc. For a die casting method, various attempts have been made to improve the fluidity of molten metal because if the flow of the molten metal (metal flow) deteriorates, defects such as minute shrinkage cavity, flow marks, etc., are likely to occur on castings. To improve the fluidity of molten metal, one method is to reduce the flow resistance of the molten metal by forming concavo-convex shapes on the surface of the die (the surface of the cavity) thereby reducing the area of contact between the molten metal and the surface of the cavity. A method to improve the fluidity of the molten metal by forming concavo-convex shapes on the surface of the cavity is disclosed, for example, in Patent Document 1. It discloses a method of die casting wherein the molten metal is poured uniformly in all parts of the cavity by having square-shaped concaves and convexes continuously spread side-by side over the surface of the cavity of the die to alternately form the parts that have high and low flow resistances and by having one side of the square-shaped concaves and one side of the convexes inclined toward the direction from which the molten metal is poured.    Patent Document: JP H07-246450
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