In the assist device, the output of an actuator is adjusted so that it becomes lower as a state of charge of a battery exceeds a first threshold value, and also so that it becomes lower as the state of charge of the battery becomes lower. The output of the actuator is controlled on the basis of the state of charge of the battery, so that it is possible to make the agent recognize the change in the state of charge of the battery by changing the output of the actuator, and as a result, to avoid the situation where the agent feels strange with respect to stopping the operation of the assist device following thereto.