Disclosed herein is an apparatus for conveying substrates, which is capable of efficiently conveying large substrates and has a function to temporarily store the substrate in a buffer unit. The apparatus includes a substrate support unit, a conveying unit, and the buffer unit. The substrate support unit supports the substrate thereon. The conveying unit sequentially conveys the substrate support unit to a plurality of processing units. The buffer unit is provided at a predetermined portion of the conveying unit to move the substrate support unit upward away from the conveying unit in a vertical direction, thus temporarily storing the substrate support unit therein while spacing the substrate support unit apart from the conveying unit. The substrate conveying apparatus thus efficiently conveys the substrates, regardless of sizes of the substrates, while temporarily storing the substrates to buffer a difference in the processing time.