In a human body detector, a wave-detection circuit for detecting waves of a resonance voltage is connected to a sensor resonance circuit that varies a constant frequency voltage in accordance with a change in the capacitance of a sensor electrode. The wave-detection circuit is connected to a differentiator that acquires a changing rate by differentiating the wave-detection voltage with respect to time, and allows a voltage to pass if the changing rate of the voltage is greater than or equal to a predetermined value. The differentiator is connected to a high-pass filter that allows passage of a voltage whose changing rate is greater than or equal to a second predetermined value. The high-pass filter is connected to a comparator whose non-inversion input terminal is connected to a power source that applies thereto a reference voltage.