The present invention provides a composite material in which a carbon material and nanoparticles are efficiently complexed, and which enables enhancement of the battery characteristics of a secondary battery.　A composite material which contains a carbon material that has a plurality of recesses and a plurality of projections, and nanoparticles that are at least partially complexed with the carbon material; and this composite material is configured such that the complexing ratio of the carbon material and the nanoparticles is 11% by weight or more.