The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a first chamber having a supply port for supplying a treating fluid; a second chamber in combination with the first chamber defining a treating space; a support member configured to support a substrate in the treating space; and a baffle unit installed in the first chamber to face the support port, and wherein the baffle unit includes: a first baffle assembly including a first baffle having first holes through which the treating fluid flow; and a second baffle assembly installed at a position farther from the support port than the first baffle assembly, and including a second baffle having second holes through which the treating fluid flow.