In this work, the growth behavior of carbon nanofibers synthesized using the liquid pulse injection technique was clarified by analyzing samples collected at different growth stages. It was confirmed that, due to the high catalytic activity of the ultrafine metal catalyst particles generated through this technique, the fibers elongate at an extremely high rate during the initial stage of growth, which leads to the high efficiency of carbon nanofiber production. Owing to this high elongation rate, the elongation process and thickening process can be practically considered as two consecutive processes. This allows the modification of the production sequence, resulting in a significant enhancement in production efficiency.