The purpose of this study was to investigate the biomechanical properties of the bony and cartilagenous elements of the sacroiliac joint. The materials were obtained from human fresh cadavers en bloc, and they were analysed on cartilage thickness, dynamic viscoelasticity, static compressive strength, and bony trabecular structure. The results were as follows: Cartilage thickness of the joint was well correlated with viscoelasticity, and the results of viscoelasticity and static compressive strength were highly equivalent to the results of analysis of the trabecular bone. The values of viscoelasticity, static compressive strength and bone area were higher in the iliac side of the joint than in the sacral side, and markedly high values were obtained in the middle part of the iliac side. In conclusion, the middle part of the sacroiliac joint may play an important role in the support and transmission of the load.