A socket wrench contains: a body including a first face, a second face, and an accommodating cavity having a stop ring arranged on the first face. A ratchet holder is accommodated in the accommodating cavity and has a polygonal groove, a first peripheral segment, a second peripheral segment, and a toothed portion. The first peripheral segment is inserted through the stop ring, the toothed portion engages with a ratchet driving device beside the accommodating cavity, and the second peripheral segment is inserted into the second face and has an elastic element fitted thereon. A clamping device includes a guiding portion having a small-diameter contacting section and a large-diameter retracting section. The small-diameter contacting section is located adjacent to the first face, and the first peripheral segment has at least one locking member moving in the polygonal groove along the small-diameter contacting section and the large-diameter retracting section.