A substrate processing apparatus is provided. The substrate processing apparatus includes a substrate chuck, a shower head structure over the substrate chuck, and a gas distribution apparatus connected to the shower head structure. The gas distribution apparatus includes a dispersion container including a first dispersion space and a gas inlet section on the dispersion container. The gas inlet section includes a first inlet pipe including a first inlet path fluidly connected to the first dispersion space and a second inlet pipe including a second inlet path fluidly connected to the first dispersion space. The second inlet pipe surrounds at least a portion of a sidewall of the first inlet pipe.