|In this study, single-lap shear tests were conducted using carbon fiber-reinforced polymer (CFRP)sheets. The parameters were the stiffness of the multi-ply CFRP sheets and bond length. Furthermore,the bond length and bond width were made larger than that in the previous experiments, in order to approach the actual reinforcement. Consequently, within the range of these tests, the debonding load increased as the number of CFRP sheet layers and stiffness increased. In addition, the three bond strengthmodels showed good agreement. It was clarified that the actual effective bond length may be longer than the effective bond length measured from the strain gauges, owing to the influence of variations in the width direction.