Various shapes of joints are used for members of traditional wooden buildings. Since these have complex stress distributions in the joints and large dispersion in the characteristics of wood, these have been used with unclear strength characteristics. In this study, tensile tests were conducted to evaluate the tensile strength characteristics of Koshikake-kama-tsugi. As a result, since it had been observed that latewood crushes earlywood in the compression surface of the joint, the compression strength of earlywood had been quantified. It was verified that the compression strength of the joint was evaluated with the compression strength of earlywood.