Carbon nanotubes have an R value of at least 1.3, where R is defined as the ratio (ID/IG) of an integral value of D band intensity (ID) to an integral value of G band intensity (IG) in the Raman spectrum. Such carbon nanotubes can be used to form a support catalyst with good catalyst activity because the surface defects on the carbon nanotubes promote improved catalyst distribution in that the support catalyst includes catalyst particles having a small mean particle size and a slight variation in particle size. Such a support catalyst has particularly useful properties when used as a catalyst layer for a fuel cell electrode.