Abstract: Microwave sensor includes an oscillator for generating microwave signals, a power divider for dividing the microwave signals, an antenna for transmitting the divided microwave signals to an outside of the microwave sensor and receiving microwave signals reflected from an object, and a mixer for detecting differences between the microwave signals received through the antenna and the signals input from the power divider and outputting Intermediate Frequency (IF) signals. The antenna includes a ground plate, an antenna pin located at a center of the ground plate, and a metallic wall formed along a circumference of the ground plate. Accordingly, the microwave sensor is advantageous in that it has uniform gain characteristics regardless of an azimuth angle by using a single antenna, functioning as both transmitting and receiving antennas, and a circuit for operating the antenna.