A socket wrench includes a wrench body, a ratchet wheel and a positioning ring. The ratchet wheel has a driving hole and a cylindrical flange extending on one side of the wrench body. The cylindrical flange has at least one aperture defined through the outer periphery thereof and communicating with the driving hole. The positioning ring is an O-shaped ring and surrounded the outer periphery of the cylindrical flange, and has a central bore. At least one protrusion radially protruded from the inner wall of the central bore of the positioning ring. The protrusion is projected from the wall of the driving hole through the aperture to position a socket. The positioning ring is moved a distance along the radial direction relative to the ratchet wheel by being pushed toward the at least one protrusion to completely retract the at least one protrusion into the aperture to release the socket.