Silk is fibrous protein material produced by silkworm and have been used as textile fiber with excellent luster, smooth texture, hygroscopicity, and mechanical strength. Recently silk has been studied as an advanced material used in various fields beyond textile fiber. Especially many papers are reported about silk material utilization as biomaterials used in medical fields based on the safety and biocompatibility from the fact which silk thread has been used as a surgical suture for long time. In this paper, a brief introduction concerning silk and silk proteins was described and then the safety and biocompatibility of silk materials were summarized from recent studies. And the utilization and the functionalization of silk materials as biomaterials were introduced from our studies. And finally cartilage regeneration study used a silk fibroin sponge material as a scaffold was described on our recent results.