In this study, carbon nanotubes (CNTs) were synthesized from size-classified catalyst metal nanoparticles to observe the effect of the nanoparticles' diameter on the diameter of the CNTs. The nanoparticles were generated by laser vaporization and classified by a differential mobility analyzer, which sorts them by diameter according to differences in electrical mobility. After classification, the nanoparticles were collected on a Si substrate. CNTs were synthesized from these catalyst metal nanoparticles by using chemical vapor deposition. This experiment synthesized mainly multi-walled carbon nanotubes (MWNTs), with a small amount of single-walled carbon nanotubes (SWNTs). The reason is thought to be that the particles' diameters were appropriate for MWNT synthesis.