A feedback control device capable of continuously performing high-accuracy, stable control even in cases where any of multiple controllers for controlling a controlled system becomes incapable of control action. A controller (master controller) generates control data for stably controlling a heater by feedback control, controls the heater in accordance with the control data, and sends the control data to the other controller (slave controller). The slave controller receives the control data from the master controller but does not control the heater while the master controller is operating normally. If the master controller develops anomaly and becomes incapable of normal control action, the slave controller initiates feedback control of the heater in accordance with the control data received from the master controller immediately before the anomaly occurred, and controls the heater thereafter in accordance with control data generated thereby.