A substrate treating apparatus includes a chamber that encloses an internal space; a susceptor in a lower part of the internal space; a shower head in an upper part of the internal space and spaced above the susceptor and that includes a plurality of distribution holes; and a blocker plate assembly that comprises a body having a plurality of intake holes that divides a space between a top wall of the chamber and the shower head into an upper intake space and a lower distribution space, a ring-shaped partition rib on an upper surface of the body, and a ring-shaped distribution unit on a lower surface of the body.