A sensor device (10) includes a sensor (31) that transmits radio waves of a predetermined frequency and receives reflected waves of the transmitted radio waves. The sensor device (10) detects presence of a moving body based on a difference between a frequency of the transmitted radio waves and a frequency of the reflected waves to activate a light source (21) in accordance with the detection. A processor (30) generates a sensor signal indicating the detection of the sensor. A determination unit (34) determines whether or not the sensor signal has an intensity that is greater than a predetermined threshold. A controller (22;35) controls activation of the light source (21) when determined that the intensity of the signal is greater than the threshold. The controller (22;35) restricts activation of the light source (21) when determined that the intensity of the sensor signal is greater than the threshold until a first specified time elapses from the determination.
