A liquid fuel property detection apparatus includes a fuel passage, a light emitting device for emitting a light including a plurality of predetermined wavelengths toward the fuel in the passage, a light receiving device for receiving the light passing through the fuel, and a calculation unit for calculating the concentration of at least one of aroma, paraffin and olefin, which are hydrocarbon component components contained in the fuel. The calculation unit calculates the concentration of a specific component, which is one of aroma, paraffin and olefin, based on the reference transmittance of light in the specific component and the actual transmittance calculated from the amount of light emitted by the light emitting device and the amount of light received by the light receiving device with respect to each wavelength of the light.