A dope is cast from a discharge opening of a casting die onto a casting drum. A casting bead is the dope between the discharge opening and the casting drum. A nozzle and a guide path are provided downstream from the discharge opening with respect to a moving direction (direction X) of the casting drum. The guide path is formed on a tapered surface of the casting die. The nozzle supplies an anticoagulant to the guide path. The anticoagulant is guided to a bottom end of the guide path. Upon reaching the bottom end, the anticoagulant forms a pool in the close vicinity of an end E of the discharge opening. The anticoagulant is securely supplied to a side edge portion of the casting bead through the pool.