PURPOSE: To manufacture cores for welt which are excellent in the flexibility and bend formability, by forming numerous core pieces by making slits in a beltlike metallic plate, and welding the core pieces to a wire, and then, by stretching the wire, when cores for welt are manufactured.

CONSTITUTION: Slits 7 which intermittently extend in the width direction of a beltlike metallic plate 2 through a connecting section 6, are formed at constant intervals in the lengthwise direction of the metallic plate 2, and numerous core pieces 8 are formed by the slits 7. A wire 9, such as piano wire, etc., is put on the upper or lower surface of the continuous core pieces 8, and the core pieces 8 are welded to the wire 9 by spot welding. Then, the core pieces 8 are separated from each other by cutting the connecting section 6, and then, the wire 9 is stretched. When the wire 9 is stretched, cores 11 having spaces 10 between each core 8 are manufactured. Thus cores which are excellent in the flexibility and which can be bent to form any shapes, are inexpensively manufactured with an excellent material yield.