To cast a formed product having thin thickness and a formed product having complicated shape with the comparatively easy method by forming the portion at least at a cavity surface side in a die with an alloy steel having a specified thermal conductivity.

A fixed die 14 and a movable die 19 are composed of base materials 14a, 19a and the portions 14b, 19b at the cavity surface side having about 5 mm thickness and metallurgically joined with the base materials 14a, 19a by using a hot hydrostatic pressing method. The base materials 14a, 19a are formed with a tool steel, etc., having 30 W/(m.K) heat conductivity at 300°C. The portions 14b, 19b at the cavity surface side are formed with a precipitation hardening type stainless steel having low thermal conductivity, such as 16-20 W/(m.K) at 300°C. A nitriding treatment on the surfaces of the portions 14b, 19b at the cavity surface side is desirably applied. In this way, the misrun generated at the starting time of a die casting can be eliminated at early time, and even if the temp. control is not stricly executed, the good product is obtd.