Provided is a buffer system for adjusting first-in first-out, more particularly, a buffer system that temporarily stores a plurality of substrates and is capable of adjusting first-in first-out. The buffer system includes one or more buffer layers having shafts and rollers fitted and fixed to the shafts so as to temporarily store or transfer substrates, a vertically moving unit moving the buffer layers up or down such that a buffer layer having thereon a substrate to be transferred is connected to a driving unit, and the driving unit rotating the shafts of the buffer layer having thereon the substrate to be transferred to transfer the substrate.