1. A controller configured to control a robot used to bond a radiation plate to an electric component via a heat conductor, the controller comprising:a machine learning device configured to learn an operating parameter for an operation of bonding the radiation plate by the robot, wherein
the machine learning device includes a processor configured to
observe, as state variables that express a current state of an environment, operating parameter data indicating the operating parameter, and heat conductor state data indicating a state of the heat conductor,
acquire determination data indicating a propriety determination result of the operation of bonding the radiation plate,
learn the operating parameter in association with the heat conductor state data, using the state variables and the determination data, and
output a command value based on the operating parameter, according to a learning result, to control the robot to bond the radiation plate to the electric component via the heat conductor based on the command value.