An inspection apparatus capable of preventing lowering of position matching accuracy. Control points are positioned in a lattice form on a scanned image of a print product, for performing position matching between the scanned image and a reference image registered in advance. An approximate line of a column and an approximate line of a row intersecting the approximate line of the column are calculated based on two or more control points positioned in the same column and the same row as one control point. One control point determined to be corrected is corrected based on the respective approximate lines of the column and the row. The print product is inspected by comparing a position-matched scanned image generated based on the control points including position-corrected control points and position-updated control points, and the reference image.