PURPOSE: To provide a manipulated variable generating device/method which can easily generate the proper manipulated variables in response to its upper and lower limit levels and also can easily cope with the changes of both limit levels.

CONSTITUTION: The upper and lower limit levels, i.e., the targets of the state quantity of a controlled system are inputted to an input means 12, and a state quantity detection means 13 detects the state quantity of the controlled system. A deviation calculation means 14 calculates an upper limit level deviation between the state quantity and its upper limit level and also a lower limit level deviation between the state quantity and its lower limit level respectively. Based on these calculated deviations, a manipulated variable generation means 15 generates a manipulated variable to control the state quantity of the controlled system. Thus both upper and lower limit level deviations are calculated for the state quantity of the controlled system, and a proper manipulated variable calculated based on both deviations. Then the proper manipulated variables are easily obtained in response to both upper and lower limit levels of the state quantity. Furthermore, it is possible to easily cope with the changes of both upper and lower limit levels of the state quantity because the manipulated variable is decided based on every limit level deviation not on the upper and lower limit levels and the absolute value of the state quantity.