<p>A backside alignment apparatus and method for determining a position relationship between a substrate (6) and a workpiece stage (24). The backside alignment apparatus includes: an illumination apparatus (1) for emanating infrared light; a workpiece stage assembly (2) for supporting and moving the substrate (6); an imaging apparatus (3) for detecting alignment marks and calculating positions of the alignment marks, the alignment marks including a reference plate alignment mark (41) and a backside alignment mark (20); and a reference plate assembly (4) for setting up a relationship between position coordinates of the imaging apparatus (3) and the workpiece stage assembly (2). The illumination apparatus (1) and the imaging apparatus (3) are able to illuminate and align different alignment marks using only one set of illumination apparatus.</p>
