A control system for a plant e.g. as a non-linear system, which is capable of properly suppressing interaction occurring between a plurality of control inputs and a plurality of controlled variables, thereby making it possible to properly control the controlled variables and easily design the control system. In the control system, each of a plurality of interaction suppression parameters for correcting the control inputs, respectively, such that the interaction is suppressed is calculated using a neural network constructed by using, out of the plurality of control inputs, a control input other than a control input corrected by a calculated interaction suppression parameter, as an input, and the interaction suppression parameter as an output.