The invention discloses a rope-driving robot arm comprising a manipulator, a lower arm body and an upper arm body. The manipulator is connected with the lower arm body through a first up-down rotating joint and a first convolution joint sequentially; the lower arm body is connected with the upper arm body through a second up-down rotating joint and a second convolution joint sequentially; the upper arm body is connected with a robot body through a third up-down rotating joint and a third convolution joint sequentially; a first rope driving mechanism used for driving the second up-down rotating joint is arranged on the lower arm body; and a second rope driving mechanism used for driving the third up-down rotating joint is arranged on the robot body. According to the robot arm, the problem that the driving force of a motor with the low price and small torque to the arm joints is insufficient is solved through the rope driving mechanisms. Meanwhile, a cleaning cloth mechanism is designed, a table top can be wiped, and the replacement period of a cleaning cloth is prolonged. The robot arm is consistent with an adult arm in size, high in flexibility, low in price, high in practicability and worthy of being popularized in the field of service robots.