A magnet embedded core is manufactured in a stable manner even when using a die clamping device having a large rated clamping force by preventing an excessive pressurizing force from being applied to a laminated iron core, performing the clamping with an appropriate pressurizing force so to minimize leakage of the resin out of magnet insertion holes, and suppressing a reduction in the geometric and dimensional precision of the laminated iron core. A die clamping device for driving a moveable platen in a direction toward and away from a fixed lower platen is configured to include a toggle link mechanism. In a fully extended state of the toggle link mechanism, an upper die abuts an end surface of the laminated iron core to close openings of the magnet insertion holes and pressurize the laminated iron core in a laminating direction.