Liquid fuel property detection system

A liquid fuel property detection apparatus comprising:

• a passage, in which liquid fuel flows;
• a light emitting device for emitting a light transversely toward the fuel in the passage, the light including a plurality of predetermined wavelengths;
• a light receiving device for receiving the light including the plurality of predetermined wavelengths, the light being transmitted through the fuel;
• and
• a calculation unit for calculating concentration of at least one specific component of aroma component, paraffin component and olefin component, which are hydrocarbon series constituent substances contained in the fuel,
• wherein the calculation unit is configured to calculate the concentration of a specific component of at least one of the aroma component, the paraffin component and the olefin component based on a characteristic of reference transmittance of the light in the specific component relative to wavelength of the light and actual transmittance of the light, which is calculated from an amount of the light including the plurality of predetermined wavelengths emitted from the light emitting device and an amount of the light received by the light receiving device.