Abstract: A transfer system includes a robot that loads and unloads a substrate to and from a cassette that accommodates a plurality of substrates in multiple stages; and a controller configured to control an operation of the robot. The robot includes: a hand that transfers the substrate, a horizontal movement mechanism that moves the hand in a width direction of the cassette in a front side of the cassette, and a lift mechanism that moves up and down the hand in the front side of the cassette. The hand includes a reflective sensor on a distal end side thereof facing the cassette to detect an object in the cassette. The controller operates the horizontal movement mechanism causing the reflective sensor to perform a horizontal scanning such that the reflective sensor facing the substrate scans in the width direction of the substrate accommodated in the cassette.