A substrate transfer system includes a substrate transfer robot disposed in a robot installment area defined between a first apparatus and a second apparatus. The first apparatus includes a first cassette, a second cassette and a first wall. The second apparatus includes a second wall. The substrate transfer robot transfers a substrate from each of the first cassette and the second cassette to the second apparatus. The substrate transfer robot includes a hand and an arm. The arm includes a first arm rotatable about a center of rotation. The first cassette is closer to the center of rotation than the second cassette. The arm moves with being partially disposed beyond the second wall in plan view and the arm moves without being disposed beyond the second wall in plan view when taking out the substrate from the first cassette.