In the initial stage of die-opening operation when an upper core 3 moves upward together with an upper die plate 1, an upper cavity die 2 is biased downwardly by an elastic member 10 so as to press the lower surface of the upper cavity die 2 against the upper surface of a lower cavity die 6 and keep their contact, thereby forcing a molded glass element 4 to remain on a lower core 5 by utilizing the difference in outside diameter between the lower core 5 and the upper core 3. This makes it possible to securely release the molded glass element 4 from the upper core 3 and leave the molded product on the lower core 5 upon die opening, enabling smooth removal and automated transportation of the molded product.