A fuel property determining apparatus may comprise a first sensor and second sensor. The first sensor may detect a concentration of an alcohol contained in fuel. The second sensor may detect a vapor pressure of the target fuel. The fuel property determining apparatus may further comprise a memory and a processor. The memory may store first data for determining a “heavy/light gravity—vapor pressure” relationship based on the concentration of the alcohol. The processor may determine the fuel property of the target fuel based on the first data stored in the memory, the alcohol concentration detected by the first sensor, and the vapor pressure detected by the second sensor.