Disclosed is a substrate with formed carbon nanotubes that are difficult to detach, that is capable of forming at high synthesizing speed carbon nanotubes connected at one end to the substrate, and a carbon nanotube composite including said substrate. The substrate for forming carbon nanotubes has a buffer layer 13, which includes aluminium atoms and fluorine atoms on at least one surface of a substrate body 14 . The carbon nanotube composite has said substrate as well as a plurality of carbon nanotubes 11, of which one ends are connected to the surface of the above aforementioned buffer layer 13.