Apparatus determines whether a stored object is a wafer alone or a frame unit formed by uniting the wafer and a ring frame. The apparatus includes first and second detecting units, the second detecting unit being stored more shallowly than the first detecting unit. The apparatus determines whether light transmitted by the first detecting unit is blocked by the object and does not reach a light receiving portion of the first detecting unit. When light transmitted from the second detecting unit is blocked by the object and does not reach a light receiving portion of the second detecting unit, the apparatus determines that the object is the frame unit, whereas when the light transmitted from the second detecting unit is not blocked by the object and reaches the light receiving portion of the second detecting unit, the apparatus determines that the object is the wafer.