Disclosed is an atomic layer deposition system and method, the system including a chamber having a first accommodation space to accommodate a first target substrate, and a first gas supplier mounted in the chamber to supply a first gas to the first target substrate, wherein the first gas supplier includes a first fixed block having a rotation space therein and including a (1-1)st passage provided in a first direction of the rotation space and a (1-2)nd passage provided in a second direction of the rotation space, and a first rotatable pipe having a first gas channel therein, having a pipe shape including at least one first gas outlet at a side thereof, and rotatably mounted in the rotation space of the first fixed block to connect the first gas outlet to the (1-1)st or (1-2)nd passage of the first fixed block.