The invention relates to a vapor grown carbon fiber having a mean fiber diameter of 80 to 500 nm, an aspect ratio of 100 to 200 and preferably a bulk density of 0.02 g/cm.sup.3 or less, wherein filaments having a diameter within .+-.20% of the mean fiber diameter occupies 65% (on a number basis) or more of the total. The production method involves thermal decomposition of a carbon source at 800 to 1,300.degree. C. in the presence of, as a catalyst, a transition metal compound having a vapor pressure of 0.13 kPa (1 mmHg) or more at 150.degree. C. and spraying of the carbon source and the transition metal compound in gas form toward the reactor inner wall to allow reaction to proceed. The vapor grown carbon fiber having a larger aspect ratio has excellent dispersibility, and when added in a resin, a smaller amount contributes to enhancement in electroconductivity and thermal conductivity, as compared with a case using conventional one.