The apparatus includes a support unit to support the substrate in a treatment space of a process chamber, a first fluid supply unit to supply a supercritical fluid having an organic solvent dissolved in the supercritical fluid, to the treatment space, a second fluid supply unit to supply the supercritical fluid having no organic solvent dissolved in the supercritical fluid, to the treatment space, an exhaust unit to exhaust the treatment space, a controller to control the first fluid supply unit, the second fluid supply unit, and the exhaust unit. The controller controls the first and second fluid supply units such that the supercritical fluid having no organic solvent dissolved in the supercritical fluid is supplied to the treatment space through the second fluid supply unit, after the supercritical fluid mixed with the organic solvent is supplied to the treatment space through the first fluid supply unit.