An apparatus for detecting abnormality for a fuel property detecting apparatus, comprising: the fuel property detecting apparatus that has a sensor part (10, 12) provided on a fuel channel (24, 30, 60) that feeds a fuel to an internal combustion engine, and detects a property of the fuel passing through the fuel channel (24, 30, 60); temperature detecting means for detecting a temperature of the fuel in a vicinity of the sensor part (10, 12); a heater (18, 26) capable of raising the temperature of the fuel in the vicinity of the sensor part (10, 12); and abnormality determining means for determining whether or not there is an abnormality in the fuel property detecting apparatus based on the temperature detected by the temperature detecting means when the heater (18, 26) is activated, wherein the abnormality determining means comprises failure determining means for determining whether or not there is a failure of the fuel property detecting apparatus itself, the sensor part (10, 12) detects a value that has a temperature dependency, the fuel property detecting apparatus comprises temperature correcting means for calculating a fuel property value by performing a correction processing for a value detected by the sensor part (10, 12) based on the temperature of the fuel detected by the temperature detecting means, and the failure determining means obtains fuel property values subjected to the correction processing at a plurality of different points of fuel temperature when the heater (18, 26) is activated, and determines whether or not there is a failure of the fuel property detecting apparatus based on the difference between the fuel property values at the different points of fuel temperature. the fuel property detecting apparatus that has a sensor part (10, 12) provided on a fuel channel (24, 30, 60) that feeds a fuel to an internal combustion engine, and detects a property of the fuel passing through the fuel channel (24, 30, 60); temperature detecting means for detecting a temperature of the fuel in a vicinity of the sensor part (10, 12); a heater (18, 26) capable of raising the temperature of the fuel in the vicinity of the sensor part (10, 12); and abnormality determining means for determining whether or not there is an abnormality in the fuel property detecting apparatus based on the temperature detected by the temperature detecting means when the heater (18, 26) is activated, wherein the abnormality determining means comprises failure determining means for determining whether or not there is a failure of the fuel property detecting apparatus itself, the sensor part (10, 12) detects a value that has a temperature dependency, the fuel property detecting apparatus comprises temperature correcting means for calculating a fuel property value by performing a correction processing for a value detected by the sensor part (10, 12) based on the temperature of the fuel detected by the temperature detecting means, and the failure determining means obtains fuel property values subjected to the correction processing at a plurality of different points of fuel temperature when the heater (18, 26) is activated, and determines whether or not there is a failure of the fuel property detecting apparatus based on the difference between the fuel property values at the different points of fuel temperature.