A machine learning device provided in a worker management device observes, as state variables representing a current state of an environment, worker external state data indicating an external state of a worker and manufacturing machine state data indicating a state of a manufacturing machine, and acquires, as label data, worker status data indicating a status of the worker. The machine learning device then learns the worker external state data and the manufacturing machine state data in association with the worker status data by performing supervised learning using the observed state variables and the acquired label data.