To provide a mold structure wherein defects such as cracks are prevented to occur by forming in a riser part a notch (cut part) having a specified depth in the direction of splitting the riser part to stress induced by the cooling shrinkage of a casting after being cast so as to allow the product constrained and restrained by the riser part to undergo cooling shrinkage by the notch formed in the riser part, releasing the internal stress induced by shrinkage restraint.

In the mold structure, a feeder head 14 is provided in a cavity 12 for casting the cast product via a pouring gate 13. In the feeder head 14, a notch 19 with prescribed depth is formed in the direction for dividing the feeder head 14 with respect to the stress direction by the cooling constraint after casting the cast product.