<div class="htmlview paragraph">In this paper the quantitative estimation on the flexural rigidity of the structural adhesive-aided joint (adhesive joint, weldbonded joint etc.) of the single-lap form in steel is carried out, based on the experiment using three-point bending test and the calculation treating the adhesive joint as the composite beam.</div> <div class="htmlview paragraph">Relationships of the flexural rigidity of the adhesive joint with its various elements and the agreement between experimental results and calculated results are in detail discussed. Moreover, factors which govern the flexural rigidity of the weldbonded joint are made clear experimentally.</div>