A doppler sensor includes a doppler signal generation unit and a determining unit. The doppler signal generation unit serves to transmit an electric wave to a detection range and receiving electric waves from a detection range, and generating a doppler signal based on a transmission signal used in transmitting the electric wave and a reception signal obtained from the received electric waves, and the determining unit serves to determine whether or not there exists a human body in the detection range through a spectrum analysis using a peak frequency, which is a frequency having the highest intensity in a difference spectrum obtained by subtracting a background spectrum from the spectrum of the doppler signal.