A microwave motion sensor including a transmitting device, a signal processing device, a signal processing device, and a path switching device is disclosed. The transmitting device transmits a microwave signal to a space under detection. The receiving device receives a reflected microwave signal reflected from the space under detection. The signal processing device processes the reflected microwave signal received by the receiving device to judge whether there is a disturbance in the space under detection, wherein the signal processing device generates the microwave signal. The path switching device is coupled to the signal processing device and the transmitting device and results in different phase shifts to a plurality of transmission paths travelled by the microwave signal.
