Provided are a composition for new bone formation and a new bone formation system, which when used to fill a bone treatment site does not effuse from the filled site due to flow of bone marrow fluid or the like, and which can promote formation of new bone at the bone treatment site. By employing a composition for new bone formation containing microparticles of a material that can emit heat in response to an external signal, and a carrier for the microparticles, formation of new bone at the bone treatment site can be promoted.
