To provide a gasoline base material allowing a car driver to enhance driving performance (responsiveness to acceleration) and to provide a gasoline composition containing this gasoline base material and allowing the driver to achieve satisfactory driving performance and excellent stability in driving.

This gasoline base material contains the fractions obtained by removing dienes from a raw material containing 4C hydrocarbon fractions obtained by catalytic cracking of hydrocarbon oil or thermal cracking of naphtha by using the hydrocarbon fractions as the raw material, applying polymerization reaction to isobutene in the 4C hydrocarbon fraction, and obtaining 8C monoolefin and 12C olefin obtained by fractionating the polymerization reaction product as the main components of the hydrocarbon fraction. The gasoline composition containing this gasoline base material is provided.