PURPOSE: To provide a manufacturing process of a core made of low melting point alloy, and prevent the deflection of wall thickness in the layer of low melting point alloy.

CONSTITUTION: A sand mold 20 for a three-dimensional shaped core is disposed in the sand molds 30, 32 for a plurality of outer molds and the wall surface 31 of the sand mold 30 for the upside outer mold and the upside of the wall surface 21 of the sand mold 20 for the three-dimensional shaped core are fixed via distance adjusting means 40, and thereafter molten low melting alloy is injected in the gap 50 between the wall surfaces 31, 32 of the sand molds 30, 32 for a plurality of outer molds and the wall surface 21 of the sand mold 20 for the three dimensional shaped core, with the result that a low melting point alloy layer 52 with uniform wall thickness is formed around the wall surface 21 of the sand mold 20 for the three dimensional shaped core.