In order to add an emergency light function to a fluorescent LED lighting device, thereby increasing safety during a power outage, this LED lighting device, which can be mounted between a pair of sockets for fluorescent lighting, is equipped with a first power supply circuit, which lights the LED using direct current power obtained by converting/rectifying alternating current power supplied from the sockets, and a second power supply circuit, which lights the LED using an embedded battery. An embedded SW controller detects that a sudden drop in the current value or the voltage value in the lighting device, from a prescribed value Von when the lighting switch is turned on to a value that is essentially zero, occurs within a prescribed time T. When the sudden drop occurs two or more times in the prescribed time (FIG. 5), it is determined that a normal operation of turning off the light has been performed, and the light is turned off, and when the sudden drop occurs only once during the prescribed time (FIG. 6), it is determined that a power outage has occurred, and the LED is lighted as an emergency light using the second power supply circuit.