To obtain a high quality cast product having uniformly dispersed grains therein by uniformly dispersing ceramic grains in molten metal, in a low pressure casting method for aluminum alloy having dispersed ceramic grains.

In the low pressure casting method which introduces the molten metal into a sprue in a metallic mold through a stoke by pressing, a casting apparatus with a gas introducing passage with a valve for introducing the gas into the inner part of the sprue in the metallic mold from the outer part, is used and the molten metal in the stoke is once pushed out into a molten metal holding vessel from the lower part of this stoke by introducing pressing gas from the gas introducing passage while maintaining airtightness in the metallic mold before pouring the molten metal. Thereafter, the molten metal is poured into the metallic mold through the stoke by closing the valve in the gas introducing passage and also, cast while exhausting the gas in the metallic mold through and exhausting passage, such as a vent hole, arranged in the metallic mold. It is preferable that inert gas is used as pressure gas and preheated to 500-700°C.