Provided is an apparatus for treating a substrate. The apparatus for treating the substrate includes: a first process chamber having a first treating space therein; a second process chamber having a second treating space therein; and an exhaust unit configured to exhaust atmospheres of the first treating space and the second treating space, in which the exhaust unit includes an integrated exhaust line in which a pressure reduction unit is installed, a first exhaust line configured to connect the first process chamber and a first point of the integrated exhaust line, a second exhaust line configured to connect the first process chamber and a second point of the integrated exhaust line, and an interference alleviation unit configured to alleviate exhaust interference between the first process chamber and the second process chamber.