A substrate treating apparatus and a substrate transporting method wherein a platform is disposed on a first ID block, and a platform is placed on a second ID block. A currently-used carrier platform is provided only on the first ID block. Accordingly, a substrate is transported in both a forward path and a return path between the first ID block and a second treating block. The substrate is returned not to the first ID block but to the second ID block disposed between the two treating blocks in the return path.