To provide the mold disjointing method which prevents a core sand in a molding from mixing with a raw molding sand when the mold is disjointed.

A molten metal is poured into a cavity 3 and an intercepting member 6 is inserted into a molten metal in a basin 5 formed in the upper mold 1 before the molten metal become solid, so that the molten metal is separated from a sprue 4, which is extending vertically. After the molten metal became solid, pull out the intercepting member 6, leaving a molding 8, containing a core piece 7 inclusive of the sprue 4, on the bottom mold 2, and up rise the upper mold 1 relatively to separate the bottom mold 2. Thereafter, the molding 8, containing the core piece 7 and the sprue 4, is disjoined from the bottom mold 2. By doing so, the core piece 7 is separated from the bottom mold 2 together with the molding 8.