A wrench with a quick rotatable driving head includes a handle, a driving head and a quick-disengaging unit. The quick-disengaging unit is composed of a fixing member secured with the driving head, an operating member inserted through the handle and fitted around the fixing member, and a restraining element transversely provided between the fixing member and the operating member and the handle. The handle and the driving head can be separated by the quick-disengaging unit so that the driving head, with the quick-disengaging unit acting as a pivot, can quickly screw or unscrew a thread locking member, and the operating member can be restrictedly positioned on the fixing member by the restraining element, able to prevent the handle and the driving head from separating.