The core mold in the molding device (51) for forming the molded member (4) of the weather strip (1) is provided with a center core (61) having a center core body (63), and a side core (62) having a pair of side core bodies (66L, 66R). The base bottom portion (21) of the molded member (4) is made so that a center slit (33) having substantially an H-shape, a pair of slide slits (32L, 32R), and slit-less bridge portion (34). In order to open the molds, the side core (62) is slid, and the center core body (63) is thereby separated from the side core bodies (66L, 66R). The center core body (63) is thereby withdrawn from the weather strip (1), and the side core bodies (66L, 66R) thereafter are withdrawn.