A robot system, comprising: a robot main body including a robot arm, an end effector attached to the robot arm, and a force sensing device configured to detect a force applied to a tip end of the end effector; and an actual reaction-force information generator configured to generate force-sensing information according to the force detected by the force sensing device, and output the force-sensing information as actual reaction-force information; characterized by a virtual reaction-force information generator configured to output a component of the force detected by the force sensing device, that has a magnitude proportional to a time differentiation value of the detected force, as virtual reaction-force information; an adder configured to output information obtained by adding the actual reaction-force information outputted from the actual reaction-force information generator to the virtual reaction-force information outputted from the virtual reaction-force information generator, as synthetic reaction-force information; an operating device to which the adder is configured to output the synthetic reaction-force information so as to make an operator sense a force according to the synthetic reaction-force information outputted from the adder, and whereby the operating device is configured to output operating information according to an operation based on a force which the operator grasps according to the synthetic reaction-force information; and a motion controller configured to control operation of the robot main body according to the operating information outputted from the operating device. a robot main body including a robot arm, an end effector attached to the robot arm, and a force sensing device configured to detect a force applied to a tip end of the end effector; and an actual reaction-force information generator configured to generate force-sensing information according to the force detected by the force sensing device, and output the force-sensing information as actual reaction-force information; characterized by a virtual reaction-force information generator configured to output a component of the force detected by the force sensing device, that has a magnitude proportional to a time differentiation value of the detected force, as virtual reaction-force information; an adder configured to output information obtained by adding the actual reaction-force information outputted from the actual reaction-force information generator to the virtual reaction-force information outputted from the virtual reaction-force information generator, as synthetic reaction-force information; an operating device to which the adder is configured to output the synthetic reaction-force information so as to make an operator sense a force according to the synthetic reaction-force information outputted from the adder, and whereby the operating device is configured to output operating information according to an operation based on a force which the operator grasps according to the synthetic reaction-force information; and a motion controller configured to control operation of the robot main body according to the operating information outputted from the operating device.