A target-travel-path generating circuit calculates a target travel path along which a controlled object can travel in the future from a current controlled object position. An ideal-control-signal calculating circuit calculates a control profile to travel along the target travel path, and a difference calculating circuit calculates a difference between an ideal control magnitude and a current control magnitude. A controller controls an operation system based on a magnitude of the difference to assist a control operation and a control-operation-state of an operator, an environment-state, and a required operation-precision. The operator receives assistance corresponding to the magnitude of the difference from an ideal control state, the control-operation-state, the environment-state, and the required operation-precision. An outputted control-operation assistance control is suitable for conditions that characterize the operator state, the environment, and the controlled object.