To develop a suitable scaffold optimizing bone regeneration, we developed bovine bone ash derived fully connected porous HA ceramic scaffolds adopting a foaming method. They revealed excellent biocompatibility. The attached cells on the scaffolds proliferated in multi-layers with osteoblastic differentiation. The bone defects grafted with bovine bone ash derived fully interconnected porous HA ceramics having average 500 μm sized spherical pores and average 150 μm sized interconnecting interpores with average 80% porosity were favorably healed without any pathologic changes within 3 weeks. New bone ingrowth with excellent osteoconduction through the spherical pores along the inner surface was noted from 1 week after implantation. Each spherical pore was filled with hematopoietic marrow and newly formed bone which with time was well integrated with the porous HA ceramic scaffold with time. These findings suggest that the bovine bone ash-derived fully interconnected porous HA ceramic formed by foaming method can be a promising bone substitute and a scaffold for bone tissue engineering.