A moving object detection system is provided with an existence detection part, an integrating part and an existence judgment part. Based on first and second detection signals, the existence detection part calculates a rotation angle of each transition factor that is obtained from the first and second detection signals and rotates around the origin in a two-dimensional coordinate system. The existence detection part is configured so that the rotation angle becomes less than 90 degrees. The integrating part integrates each rotation angle to obtain an integrated angle. The existence judgment part judges whether or not a moving object approaching or leaving a receiver of the device exists in a detection area based on the integrated angle and a threshold angle.