To detect a marker in a liquid residue obtained by evaporating a sample and enable the identification of a hydrocarbon composition, by incorporating a specific marker into a gasoline.

A marker which has a number-average mol.wt. of 15,000 or higher and a weight-average mol.wt./number-average mol.wt. ratio of 1.5 or lower, is soluble in a hydrocarbon composition to be identified, does not impair hydrocarbon filterability, neither vaporizes nor thermally decomposes at 120°C and lower, and does not cause an engine trouble is added to a gasoline in an amount of up to 1.0 ppm.