A stop device is provided for a vehicle slide door for an opening of a vehicle side body structure. The slide door is guided in a front-to-rear direction by a sliding door mechanism which moves the slide door on a rail fixed to the side body structure. The stop device comprises a bracket for securing to the side body structure near a rear end of the lower rail. The bracket includes a base having a forward end portion and a rear end portion. A full stopper is mounted to the rear end portion of the bracket, and a mid-stopper is mounted to the forward end portion of the bracket. A strengthening member is connected to and extends at least partially outwardly from the base. The strengthening member is provided at least partially below the full stopper. The strengthening member has a generally stepped configuration.