The invention provides a machine learning device, a robot system, and a machine learning method. The machine learning device that learns an operation of a robot (14) for picking up, by a hand unit, any of a plurality of workpieces (12) placed in a random fashion, including a bulk-loaded state, includes a state variable observation unit (21) that observes a state variable representing a state of the robot, including data output from a three-dimensional measuring device (15) that obtains a three-dimensional map for each workpiece, an operation result obtaining unit (26) that obtains a result of a picking operation of the robot for picking up the workpiece by the hand unit, and a learning unit (22) that learns a manipulated variable including command data for commanding the robot to perform the picking operation of the workpiece, in association with the state variable of the robot and the result of the picking operation, upon receiving output from the state variable observation unit and output from the operation result obtaining unit.