A cable arrangement for a robot arm is provided, which includes a rotation arm and a line member such as a power cable. The rotation arm has a front end and a base end, the front end being provided with a swing shaft, the base end being provided with a rotational shaft rotatable about a longitudinal axis. The line member extends from the base end toward the front end of the arm. The rotational shaft includes a line offset member formed with at least one through-hole for passing the line member. The through-hole as a whole is offset from the axis of the rotational shaft.