Disclosed is a substrate treating apparatus including a chamber having a process space therein in which a substrate is treated, a substrate support assembly located in the chamber and including a support plate that supports the substrate, a gas supply unit that supplies gas into the chamber, a gas distribution plate that distributes the gas and supplies the gas into the process space, and a temperature control unit that controls temperature of the gas distribution plate. The temperature control unit includes a heating member that heats the gas distribution plate, a cooling member that cools the gas distribution plate, and a control member that controls the heating member and the cooling member, based on a correlation coefficient regarding an interaction of the heating member and the cooling member and a disturbance coefficient regarding an external influence.