A manipulated variable calculator having a plurality of control loops and configured to calculate manipulated variables to be respectively given to a plurality of temperature adjusters includes: a reference model output generator configured to generate a reference model that is a response output until reaching a temperature setpoint when, in the plurality of control loops, a manipulated variable of a control loop having the slowest response speed is defined as 100%; a simulator configured to sequentially search for a switching time to determine a manipulated variable pattern; a reference model configured to generate a reference model output based on the searched switching time; and a control switching unit configured to switch to a feed-back control using an error between the reference model outlet and the temperature setpoint when the reference model outlet reaches a predetermined time or a predetermined temperature after the reference model outlet starts.