Materials with bioactivity, i.e. bone-bonding ability, form a bone-like apatite layer on their surfaces in the body and bond to living bone through this bone-like apatite layer. Bone-like apatite is carbonated hydroxyapatite with small crystallites and low crystallinity. The coating of the bone-like apatite layer on the substrates is expected to be a useful technique to induce bioactivity on the substrates. The bone-like apatite layer can be formed on the surface of substrates in a solution mimicking body fluid when some functional groups are introduced to the substrates. This process is called a biomimetic process. Coating of bone-like apatite layers through this biomimetic process has received much attention in the fabrication of novel composites with bioactivity. An overview of the coating of bone-like apatite is described.