Collagen accounts for about 30 percent of whole body protein, and it is distributed throughout the body. In terms of food, denatured collagen is called gelatin, and gelatin hydrolysate with the protease is used as a functional food material. This hydrolysate is called “collagen peptide”. On the other hand, recent Japanese women uptake about 2g of collagen from meals every day, and some people uptake about 5-10g collagen peptide from a dietary supplement every day.   Collagen peptide, a heterogeneous mixture of oligopeptides and polypeptides similar to gelatin, has been used therapeutically as a dietary supplement to improve conditions of joints and articular cartilage. Some experiments have suggested that oral ingestion of collagen peptide might have beneficial effects on joint conditions such as osteoarthritis. Moreover, oral intake of collagen peptide induced the elevation of serum levels of collagen dipeptide, such as prolylhydroxyproline (Pro-Hyp). As peptide bond of Pro-Hyp is hard to digested by the specific protease in the body. In recent years, such as the improving effect of articular cartilage, bone and skin function of collagen peptide and the dipeptide of the specific sequence of collagen peptide detected from the blood after collagen peptide intake have been well reported. Additionally, the food safety of collagen peptide also should be discussed. The food function and bioactive mechanisms of collagen peptide is becoming clear.