A sintered material excellent in thermal stress and bonding strength; a connection structure containing the sintered material; a composition for bonding with which the sintered material can be produced; and a method for producing the sintered material. The sintered material has a base portion, buffer portions, and filling portions. The buffer portions and filling portions are dispersed in the base portion. The base portion is a metal sintered body, each buffer portion is formed from a pore and/or material that is not the same as the sintered body, and each filling portion is formed from particles and/or fibers. The sintered material satisfies A>B. A is the kurtosis of volume distribution of the base portions in a three-dimensional image of the sintered material. B is the kurtosis of volume distribution of the base portions in a three-dimensional image of the sintered material from which the filling portions are removed.