To establish the diagnosis of osteoporosis from the mechanical integrity viewpoint, not only bone mineral density (BMD) but also in vivo architecture of bone is essentially needed. A new visualization technique of the trabecular bone is presented. We analyzed numerically the A-mode signals from the transducer for medical use to distinguish whether bone substance or bone marrow. This is based on the damping curve and the threshold line as bone substance. The technique allowed visualizing the architecture to the depth about 10 mm from the bone surface. We demonstrated the validity of this technique using bovine cancellous bone and a ceramic specimen with spongy architecture.