The inventive concept provides an apparatus and a method for heat-treating a substrate. The method includes a first treatment operation of spacing a substrate apart from a support plate provided with a heater to a first height in a state in which a treatment space, in which the substrate is treated, is closed and heating the substrate, a second treatment operation of, after the first treatment operation, lowering the substrate such that the substrate is located at a second height and heating the substrate, a third treatment operation of, after the second treatment operation, lifting the substrate such that the substrate is spaced apart from the support plate to be located at a third height and heating the substrate, and a fourth treatment operation of, after the third treatment operation, lowering the substrate such that the substrate is located at a fourth height and heating the substrate.