A percent body fat measuring apparatus includes a first and a second electrodes with which a living body is brought into contact, a detection resistor of which one terminal is connected to the second electrode, signal generator which produces a measurement signal and applies a produced measurement signal between the first electrode and the other terminal of the detection resistor, level detector for detecting the level of a signal which develops between the terminals of the detection resistor and is an object of detection, and percent body fat computer for determining percent body fat on the basis of a result of detection operation performed by the level detector. A measurement signal produced by the signal generator is made analogous to a half-wave waveform, and the level detector detects the level of a waveform analogous to a half-wave of the signal to be detected.