A string stopper includes a fixing hole formed at an end, and a guide hole formed at one side of the fixing hole. A string is inserted into the fixing hole so that a fixed end of the string is fixed to the fixing hole, and a free end of the string is inserted into an entrance of the guide hole and is drawn out of an exit of the guide hole. The guide hole has a first narrow groove and a second narrow groove which are respectively formed at the inside of the entrance and at the outside of the exit of the guide hole.