A casting device includes a mold provided with an insert die, a molten metal supply device for supplying molten metal into the mold, and a gas supply mechanism for supplying a gas, which is used for forced cooling, to the insert die. The insert die is made of tungsten having a thermal conductivity significantly higher than that of die steel. The insert die has a spiral or meandering gas passage therein. The spiral or meandering gas passage has a passage length much longer than a straight passage.