An LED lamp (1) is employed in a state mounted on a lighting fixture. The LED lamp (1) includes an LED source portion (2) including a plurality of LED chips, an illuminance sensor module (12) detecting ambient illuminance, and a controller controlling the LED source portion (2) in response to illuminance of ambient light other than light emitted by the LED source portion (2) on the basis of an output signal received from the illuminance sensor module (12) when the LED source portion (2) is in a lighting-up state. When the LED source portion (2) is in the lighting-up state, there is a possibility that the illuminance sensor module (12) detects not only the ambient light illuminance but also spontaneous light illuminance. The controller eliminates influence by the spontaneous light illuminance, and controls the LED source portion (2) in response to the illuminance of the ambient light.