A mold die includes: a mold die body that is configured to hold an object to be molded, the object including a substrate and a chip mounted in a central area of the substrate, and that has a cavity which is rectangular in a plan view and which is configured to receive a resin material, the mold die body including: a pot for containing the resin material; a gate disposed at one side of the cavity and configured to allow the resin material to flow into the cavity; and a flow-path restricting mechanism that is disposed on both lateral sides of the cavity that are perpendicular to the one side and that is configured to narrow lateral flow paths, the lateral flow paths being flow paths for the resin material flowing through the cavity in which the chip is not disposed.