An apparatus for treating a substrate includes a light treatment chamber having an interior space, a support unit that supports the substrate in the interior space, and an irradiation unit that irradiates light to the substrate in the interior space to remove organic matter remaining on the substrate, in which the irradiation unit includes a first light source that irradiates first light to the substrate and a second light source that irradiates, to the substrate, second light having a different wavelength range from the first light.