An imaging device that captures an image of a specific region containing a boundary between an outer edge of the bead filler and a support body; an image processing device that detects an edge corresponding to the boundary between the outer edge of the bead filler and the support body based on an image captured by the imaging device, and that computes distances between a reference model line, that runs along the rotation direction of the support body and is determined based on a detected edge, and each respective point on the edge present in a region containing a join portion; and a control device that performs good/no-good determination on the join portion based on the distances between the reference model line and each of the points on the edge.