An apparatus has a first electrode group (1) including at least one electrode and arranged on the abdominal surface of a subject (human) with the navel of the subject serving as a reference position, a second electrode group (2) including at least one electrode and arranged on the back surface of the subject, a third electrode group (3) including at least two electrodes and arranged on the surface of the subject at an intermediate position between the first and second electrode groups (1, 2), and a controller (8) to supply a current between an electrode selected from the first electrode group (1) and an electrode selected from the second electrode group (2), measure a voltage generated between two electrodes of the third electrode group (3), and compute an abdominal fat quantity of the subject according to the measured voltage.