A moving object detecting apparatus includes: a transmitting/receiving unit for radiating an ultrasonic wave and receiving a reflective wave reflected from an object present in a monitoring space; a phase detection circuit for mixing reference signals with a reflective signal and obtaining a pair of Doppler signals each having an amplitude depending on a phase difference from the reference signal, each of the Doppler signals having a different phase from each other; a rotation angle calculation unit for calculating a rotation angle; a cumulative addition unit for accumulating the rotation angle; and a comparison unit for comparing the accumulated rotation angle with a threshold value. In the moving object detecting apparatus, a single ultrasonic vibrator is commonly used in the transmitting unit and the receiving unit.