The carbon nanofiber has a content of oxygen controlled in a range of 8% by mass to 20% by mass and excellent dispersibility in polar solvents by means of an oxidization treatment carried out on a raw material of the carbon nanofiber. The above-described oxidization treatment is preferably carried out at 100° C. or higher using an mixed acid of nitric acid and sulfuric acid in which the nitric acid concentration is in a range of 10% by mass to 30% by mass. A carbon nanofiber dispersion liquid is obtained by dispersing the above-described carbon nanofiber in a polar solvent, and a carbon nanofiber composition contains the above-described dispersion liquid and a binder component.