A molding device for vacuum casting a metal ingot is provided. The mold includes a mold cavity defined by an ingot mold, a core and a bottom. The mold is arranged inside a vacuum-cast enclosure and includes a source of introducing molten metal at the upper portion thereof. A distribution device for receiving and distributing molten metal, which is suitable for receiving the molten steel introduced into the vacuum-cast enclosure and for redistributing the molten metal in the mold cavity, is arranged at the upper portion of the mold cavity. The molten metal is introduced into the enclosure so as to form a first jet of molten steel under a vacuum, in order to pour the molten metal over the distribution device and to form at least one second jet of molten steel under a vacuum, which originates with the distribution device and terminates in the mold cavity so as to fill the mold cavity with molten metal.