Weather strip, manufacturing method thereof and molding device

A weather strip (1) includes extruded parts (2,3) and a molded part (4). In the molded part which corresponds to an upper corner part, a slit is formed in a base portion thereof for ease of the removal of a core mold. The slit is provided with a first slit (31) and a second slit (32), and an integral bridge portion (33) is provided between those slits. The second slit is formed so as to extend through an inner corner portion. The existence of the bridge portion obviates the necessity of bonding and this obviates further the necessity of making allowance for an extent of deformation associated with the closure of the slit portion. In addition, the implementation of removal work of the core mold can be facilitated.