Provided is a substrate treating apparatus. The substrate treating apparatus comprises: a support unit provided to support the substrate and rotate the substrate; a treatment liquid nozzle for supplying the treatment liquid onto the substrate supported by the support unit; a pre-wet liquid nozzle for supplying a pre-wet liquid onto a substrate supported by the support unit; and a controller for controlling the treatment liquid nozzle and the pre-wet liquid nozzle, wherein the controller controls the treatment liquid nozzle and the pre-wet liquid nozzle to perform a pre-wet step for supplying the pre-wet liquid to the substrate, and then a treatment liquid supply step for supplying the treatment liquid to the substrate and supplying the pre-wet liquid to the substrate during the supplying the treatment liquid to the substrate.