A roof side weather strip has an upper side portion, a vertical side portion and a corner portion. The vertical side portion has a mounting base portion which is to be mounted on a pillar, a hollow seal portion which is formed on a vehicle-interior inner surface of the mounting base portion and is adapted to be brought into abutment with a door glass, and a seal lip portion which is formed on a vehicle-exterior inner surface of the mounting base portion adjacent to a vehicle-interior side of the hollow seal portion and is adapted to be brought into abutment with a vehicle-interior side surface of the door glass. A groove portion is formed between the hollow seal portion and the seal lip portion, and a water stopping rib is formed in a portion in the groove portion which constitutes a portion on the corner portion which lies in the vicinity of the vertical portion or a portion on the vertical side portion which lies in the vicinity of the corner portion.