FUEL SHORTAGE DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE, STRADDLED VEHICLE, AND FUEL SHORTAGE DETECTION METHOD FOR INTERNAL COMBUSTION ENGINE

A fuel shortage detection device for an internal combustion engine capable of detecting fuel shortage based on the air-fuel ratio of the exhaust gas. The fuel shortage detection device for an internal combustion engine includes: an air-fuel ratio determination section 61 that determines whether the air-fuel ratio of the exhaust gas is equal to or greater than a first threshold value TH1 based on the detection result of an O2 sensor 78; an accumulated time calculation section 62 that calculates an accumulated time Ta, which is an amount of time over which the air-fuel ratio is equal to or greater than the first threshold value TH1; an accumulated time reset section 63 that resets the accumulated time Ta at every predetermined time interval B; an accumulated time determination section 64 that determines whether the accumulated time Ta is greater than or equal to a second threshold value TH2; and a fuel shortage determination section 67 that determines that there is fuel shortage when the accumulated time Ta becomes equal to or greater than the second threshold value TH2.