It is generally accepted that more than 10(-6) gauss order magnetism was not detected in normal human condition. However, we detected 10(-3) gauss (mGauss) order bio-magnetic field strength from the palm in special persons who emitted External Qi ("Chi" or "Ki"). This detection was possible by special arranged magnetic field detection system, consisted of a pair of 2 identical coils with 80,000 turns and a high sensitivity amplifier. Each of the coils were rolled 80,000 turns accurately, and were connected in series in opposite direction, actuating as a gradiometer. We measure bio-magnetic field strength in 37 subjects with this detection system. The only 3 subjects of them exhibited strong bio-magnetic field of 2 to 4 mGauss in frequency range of 4 to 10 Hz. This magnetic field strength was greater than that of normal human bio-magnetism by 1,000 times at least. A simultaneous measurement of bio-magnetic field strength and its corresponding bio-electric current was examined in one subject. During exhibiting such strong bio-magnetism, its corresponding electric current was not detectable. Therefore, the extra-ordinary large bio-magnetic field strength can not derive from internal body current alone, hence the origin of the large bio-magnetism is still unknown. We suppose that the extraordinary large bio-magnetic field strength might be originated from "Qi" energy in the oriental medicine or in the oriental traditional philosophy.