Abstract: A stepless wrench includes a wrench head, a toothless drive, an overrunning mechanism. The wrench head has a central bore and a cavity both defined in a front surface thereof. The cavity has a curved wall that has an engaging section and a releasing section. The toothless drive is rotatably carried in the central bore of the wrench head and has an outer cylindrical peripheral surface. A distance between the toothless drive and the curved wall of the cavity gradually decreases in a direction from the releasing section toward the engaging section. The overrunning mechanism has a roller and an elastic member both received in the cavity of the wrench head. The roller is biased by the elastic member, and has a diameter greater than a distance between the engaging section and the toothless drive such that the roller is sandwiched in between the toothless drive and the curved wall of the cavity.