The present disclosure relates to a substrate processing apparatus, and more specifically, to a substrate processing apparatus capable of blocking the introduction of external air and external particles into a chamber by forming an air curtain at a loading/unloading part when the chamber is open. The substrate processing apparatus of the present disclosure includes a chamber in which a space is formed, and a fluid injection part configured to inject a fluid from an outer side of a substrate loading/unloading part of the chamber through which a substrate is loaded and unloaded.