A machine learning device learning a movement of a robot where a human and the robot collaboratively work includes: a state observation unit observing a state variable representing a state of the robot when the human and the robot collaboratively work; a reward calculation unit calculating a reward based on control data for controlling the robot, the state variable, an action of the human, and a facial expression of the human; and a value function update unit updating an action value function for controlling a movement of the robot, based on the reward and the state variable.
MACHINE LEARNING DEVICE, ROBOT SYSTEM, AND MACHINE LEARNING METHOD