<p>An optical current transformer in which an influence of a temperature change in a magneto-optic sensor unit is compensated to conduct measurements with high accuracy by the following structure: Between two polarizers 4 and 5 having mutually different transmission polarized light directions, a Faraday rotator 6 is disposed to form a magneto-optic sensor unit. Light beams from optical transmission units 2 and 2' are inputted to the magneto-optic sensor unit in opposite directions. Two light sources 7 and 7' for emitting the input light beams emit light beams having the same waveform characteristics. Light beams outputted from the magneto-optic sensor unit are converted to electric signals by photoelectric conversion units 8 and 8'. Two light beams traveling through the magneto-optic sensor unit in mutually opposite directions are subjected to intensity modulation by using mutually different frequencies. From the electric signals after photoelectric conversion, intensity-modulated frequency components are selectively extracted. The change of quantity of light caused in two light beams by the Faraday effect is derived by differential computation. <IMAGE></p>
