A wrench having two driving stems pivotally connected with each other. One of the driving stems has a main stem and a female joint protruding from a rectangular or cylindrical section of the main stem with a hole at a center thereof. The other driving stem has the other main stem and a male joint projecting out of the center of a rectangular or cylindrical section of the main stem. The male joint and the female joint are engaged with each other via a coupler such as a roll pin. Therefore, without using an additional hinge or other mechanical coupler, these two driving stems are pivotally connected with each other.