A control system for a plant is provided. This control system can control the plant more stably, when the model parameters of the controlled object model which are obtained by modeling the plant, which is a controlled object, are identified and the sliding mode control is performed using the identified model parameters. The model parameter identifier (22) calculates a model parameter vector (θ) by adding an updating vector (d θ) to a reference vector (θ base) of the model parameter. The updating vector (d θ) is corrected by multiplying a past value of at least one element of the updating vector by a predetermined value which is greater than “0” and less than “1”. The model parameter vector (θ) is calculated by adding the corrected updating vector (d θ) to the reference vector (θ base).