The present invention aims to coaxially aligning a tire with support rims with high accuracy by eliminating an effect of a tread outer surface.A radial inner end position of the bead portion of the tire his detected by a photoelectric sensor at circumferentially separated four points, and a deviation between the central axis of the tire and the central axis of a pair of support rims. The bead portion of the tire, which is an subject of the detection of the inner end position, is a portion where its dimension and shape are hardly changed even if the tire runs (i.e., is used) for a long time, so that the above-mentioned deviation can be determined at a high accuracy to, thereby, conduct a center alignment of the tire with the support rims at a high accuracy.