Abstract: A substrate treating apparatus and a cleaning method thereof that can clean a nozzle tip and its surroundings in the presence of a source of contamination are provided. The substrate treating apparatus includes: a substrate support unit supporting a substrate; a spraying unit including a nozzle tip member, which has an outlet formed at an end thereof, and ejecting a treating solution onto the substrate using the nozzle tip member; and a standby port accommodating the nozzle tip member that has completed the ejection of the treating solution, wherein the substrate treating apparatus cleans the nozzle tip member and the inside of the standby port before the nozzle tip member sucks back a second chemical solution.