To align a substrate with a rotary treating device by confirming the existing position of the substrate without rotating the substrate.

The position of the edge of a wafer 11 in the direction perpendicular to the advancing direction of the wafer 11 is successively detected while the wafer is advanced by a prescribed unit amount in a state where a rotatable spin chuck 12 is maintained in a standstill state. By successively comparing the magnitude of the position of the edge detected at the preceding time with that of the position of the edge detect at the succeeding time, the position of the edge detected when the compared results turn to a decreasing trend from an increasing trend is detected as the position of the center of the wafer 11 and the wafer 11 is positioned based on the recognized position of the center.