A robot arm control system comprising: a robot arm provided in a manner capable of moving in a given space; a motor for operating the robot arm; a torque adjustment device for operating in a manner capable of adjusting a transmitted torque that is transmitted from the motor to the robot arm; a control device for performing operation control of the robot arm; and an external force detection device for detecting an external force acting on the robot arm, wherein the robot arm is provided with a gravity-compensating mechanism for cancelling an effect of gravity due to the robot arm, and wherein the control device is configured to issue a command for adjustment of the transmitted torque at the torque adjustment device, without taking into account the effect of the gravity of the robot arm, wherein the torque adjustment device includes an input unit joined on the motor side so as to be rotatable by driving of the motor, an output unit rotatably joined on the robot arm side, and a transmission unit disposed between the input unit and the output unit in a manner capable of transmitting power from the input unit to the output unit, wherein the torque adjustment device is configured such that, when an input torque due to rotation of the input unit is at or below a given torque limit value, the input unit and the output unit rotate in an integrated manner to cause a value of an output torque, which is output from the output unit to the robot arm, due to rotation of the output unit to be approximately the same as a value of the input torque, and when the input torque exceeds the torque limit value, the value of the output torque is reduced compared with the value of the input torque by slippage allowing relative rotation between the input unit and the output unit, wherein the control device is configured to issue a command to the torque adjustment device to adjust the transmitted torque, according to a desired operation mode of the robot arm, wherein the control device is configured to allow selection of control according to a plurality of control modes, the plurality of control modes including a first control mode, in which operation control of the motor and the torque adjustment device is performed for detection of the external force by the external force detection device, and wherein the external force detection device is configured to determine the external force based on slippage of the torque adjustment device based on the control in the first control mode. a robot arm provided in a manner capable of moving in a given space; a motor for operating the robot arm; a torque adjustment device for operating in a manner capable of adjusting a transmitted torque that is transmitted from the motor to the robot arm; a control device for performing operation control of the robot arm; and an external force detection device for detecting an external force acting on the robot arm, wherein the robot arm is provided with a gravity-compensating mechanism for cancelling an effect of gravity due to the robot arm, and wherein the control device is configured to issue a command for adjustment of the transmitted torque at the torque adjustment device, without taking into account the effect of the gravity of the robot arm, wherein the torque adjustment device includes an input unit joined on the motor side so as to be rotatable by driving of the motor, an output unit rotatably joined on the robot arm side, and a transmission unit disposed between the input unit and the output unit in a manner capable of transmitting power from the input unit to the output unit, an input unit joined on the motor side so as to be rotatable by driving of the motor, an output unit rotatably joined on the robot arm side, and a transmission unit disposed between the input unit and the output unit in a manner capable of transmitting power from the input unit to the output unit, wherein the torque adjustment device is configured such that, when an input torque due to rotation of the input unit is at or below a given torque limit value, the input unit and the output unit rotate in an integrated manner to cause a value of an output torque, which is output from the output unit to the robot arm, due to rotation of the output unit to be approximately the same as a value of the input torque, and when the input torque exceeds the torque limit value, the value of the output torque is reduced compared with the value of the input torque by slippage allowing relative rotation between the input unit and the output unit, wherein the control device is configured to issue a command to the torque adjustment device to adjust the transmitted torque, according to a desired operation mode of the robot arm, wherein the control device is configured to allow selection of control according to a plurality of control modes, the plurality of control modes including a first control mode, in which operation control of the motor and the torque adjustment device is performed for detection of the external force by the external force detection device, and wherein the external force detection device is configured to determine the external force based on slippage of the torque adjustment device based on the control in the first control mode.