Two current electrodes 2 and 3 are arranged on a circumference of a subject 1, a distance between the two current electrodes being sufficiently shorter than a circumferential length of the subject 1. A current source 4 passes a current between the two current electrodes. A measuring electrode 5 is arranged adjacent to one of the two current electrodes 2 and 3. A measuring electrode 11 is arranged substantially opposite to the two current electrodes 2 and 3 across the subject 1. A voltmeter 7 measures a voltage generated between the measuring electrodes 5 and 11. A body fat computing unit 25 computes the quantity of subcutaneous fat 8 of the subject 1 according to the voltage measured with the voltmeter 7.