A moving object detection apparatus comprises a transmitter, a receiver, a detection portion, a binary conversion portion and a judgment portion. The transmitter emits energy waves with a first frequency to a detection area. When receiving incoming energy waves from the detection area, the receiver generates an electric signal corresponding to the incoming energy waves. The detection portion obtains a detection signal from a reference signal with the first frequency and the electric signal. The binary conversion portion compares the detection signal with a conversion threshold signal to obtain a binary signal. The judgment portion judges whether or not a moving object approaching or leaving the receiver exists in the detection area based on the binary signal.