A substrate transfer apparatus to transfer a circular substrate provided with a cutout at an edge portion thereof, includes: a sensor part including three light source parts applying light to positions different from one another at the edge portion, and three light receiving parts paired with the light source parts; and a drive part for moving the substrate holding part, wherein the three light source parts apply light to the light receiving parts so that whether or not a detection range of the sensor part overlaps with the cutout of the substrate is determined on the basis of an amount of received light by each light receiving part, and when it is determined that there is an overlap at any position, positions of the edge portion of the substrate are further detected with the position of the substrate displaced with respect to the sensor part.