Embodiments of the inventive concept relate to a substrate treating apparatus. A substrate support unit configured to support a substrate includes a support plate, on which the substrate is positioned, the support plate may include a passage formed on an upper surface of the support plate and connecting a central area and a side surface of the support plate, and a recess formed in a peripheral area of the support plate and recessed inwards from a side surface of the support plate, and the recess may communicate with one end of the passage.