PURPOSE: To obtain the subject carbon fiber effective in remarkably improving the dispersibility and compoundability to a heat-resistant resin and capable of giving a uniform composite material having excellent properties by grafting more than specific amount of polyester component to a whisker-like carbonaceous fiber.

CONSTITUTION: The surface of a whisker-like carbonaceous fiber is metallized and then subjected to the addition reaction with a polymerizable organic monomer having unsaturated group and ester group (e.g. methyl methacrylate). The grafted carbonaceous fiber whisker is introduced into a conventional system for the synthetic reaction of polyester and subjected to addition reaction to add >500mg of the ester component to 1g of the whisker-like carbonaceous fiber. The obtained fiber has remarkably improved dispersibility and compoundability especially to a polyester resin and heat-resistant resin and sives a composite material having high uniformity and excellent properties.