Disclosed are an apparatus and a method for liquid-treating a substrate. An apparatus for treating a substrate includes a liquid treatment chamber that supplies a liquid onto the substrate to liquid-treat the substrate, a drying chamber that removes the remained liquid on the substrate, and a transfer unit that transfers the substrate between the liquid treatment chamber and the drying chamber, wherein the transfer unit includes a hand that supports the substrate, and a weight measuring unit that measures a weight of the remained liquid on the substrate. A weight of a remained liquid on a substrate may be measured by measuring a weight of the substrate while the substrate is transferred.