A bio-signal measuring apparatus includes a first electrode, a second electrode, a third electrode, a fourth electrode, and a first circuit network and a second circuit network, each of the first circuit network and the second circuit network includes one or more resistances. The bio-signal measuring apparatus further includes an impedance measurer configured to measure a first impedance of the first circuit network in a first correction mode, measure a second impedance of the second circuit network in a second correction mode, measure a third impedance of an object in a first measurement mode, using the first electrode, the second electrode, the third electrode, and the fourth electrode, and measure a fourth impedance of the object in a second measurement mode, using the first electrode, the second electrode, the third electrode, and the fourth electrode.