A fan failure detector for detecting whether a fan is locked with a drive IC, a coil and an inspection circuit, the drive IC outputting a pulse signal, the coil is electrically connected to the drive IC and driven by the drive IC, the inspection circuit is electrically connected to the drive IC and the coil, the inspection circuit includes an RC charge/discharge circuit, a diode, a second capacitor, a voltage divider and a transistor having an output terminal, wherein the RC charge/discharge circuit, the diode, the voltage divider and the transistor are sequentially connected in series, the second capacitor is electrically connected with the diode and the voltage divider, when the fan operates normally, the output terminal provides a low voltage signal, when the fan locks, the output terminal provides a high voltage signal to avoid a wrong judgment that the fan still operates normally.