An illumination apparatus includes a light source; a sensor which has an image sensor and detects an illuminance and a presence of a human based on a captured image while setting a range overlapping a range illuminated by the light source as a visual field; an illuminance determining unit for varying a light output from the light source based on the illuminance and the presence of a human; and a dimming control unit. The illuminance determining unit obtains an illuminance of an illuminance maintaining area included in the visual field based on the captured image, and when the sensor detects no human, the illuminance determining unit reduces the light output while maintaining the illuminance of the illuminance maintaining area to be equal to or greater than a threshold that is set in advance as a lower limit illuminance, which makes it feasible for the image sensor to capture an image.