To provide a moving object detector that accurately detects a case where a person approaches and a motion of leaving and outputs a determination result with a simple output signal.

A moving object detector comprises: a phase difference arithmetic processing section 41 for operating a mutual phase difference from I-phase output and Q-phase output of a doppler sensor section 14a and outputting the obtained phase difference with voltage information with either positive or negative polarity; a dead-band processing section 42 for outputting no voltage signal when an absolute value of the output voltage is equal to or less than a predetermined value; a pair of comparators 52a and 52b for, when the output voltage information has negative polarity, determining that there is an approaching object and outputting an "H" signal from a first output section 43a, and when the information has positive polarity, determining that there is a leaving object and outputting the "H" signal from a second output section 43b; and an adder circuit 51 for applying an offset voltage to let a change in voltage output by the dead-band processing section 42 be a change in voltage with positive polarity.