PURPOSE: To obtain the casting mold for runner accurately and highly efficiently by assembling a vane pattern made of vinyl chloride or other on a molding board to make a core, heating the core to the specified temperature then drawing the vane pattern from the core.

CONSTITUTION: A thermoplastic resin plate 2 such as of vinyl chloride which is cut out to vane form and has been heated to soften to above the softening temperature of the resin is placed on a runner vane original mold 1 made of wood mold and is allowed to make a good fit to the mold 1, whereby the vane pattern 4 is obtained. Next, the pattern 4 is fixed on a molding board 3 in compliance with the lines scribed thereon. The measurement of clearances is accomplished by inserting a measuring gauge 5. A profile measuring gauge or the like may be used as well. Local bending, correcting, etc. are performed by a burner and the like to make accurate dimensions. A core grid is set and the core molding is performed by an ordinary method, after which the molding is removed from the molding board 3 and is then heated, thence softened vane pattern 4 is drawn out. In this way, the reliable core is obtained.