A porous structure or surface-roughened structure impregnated with fine bone powder is usable as an artificial bone or artificial dental root. The porous structure has communicating macro-pores having an average diameter of 100-1000 .mu.m open on its entire outer surface at a density of 1 or more per an area of 1000 .mu.m.times.1000 .mu.m, and fine communicating pores or recesses having an average diameter of 0.005-50 .mu.m open in the communicating macro-pores at a density of 1 or more per an area of 50 .mu.m.times.50 .mu.m. The surface-roughened structure has fine recesses having an average diameter of 0.005-50 .mu.m and an average depth of 0.005-50 .mu.m open on its entire outer surface at a density of 1 or more per an area of 50 .mu.m.times.50 .mu.m.