The inventive concepts relate to an apparatus for treating a substrate. The apparatus includes a container having a treatment space of which a top end is opened, a rotatable support unit supporting a substrate disposed within the treatment space, a heating unit heating the substrate supported by the support unit, and a fluid supply unit supplying a fluid to the substrate disposed on the support unit. The heating unit includes a plurality of heaters installed in a plurality of zones of the support unit, respectively, and a controller controlling the plurality of heaters. The controller controls the plurality of heaters by a first mode until the plurality of zones reach a target temperature, and the controller controls the plurality of heaters by a second mode different from the first mode after the plurality of zones reach the target temperature.