Abstract: An optical fiber electric current sensor includes a polarization-splitter (13) that splits light outputted from a sensor fiber (11) into two polarization planes of which polarization directions are perpendicular to each other, a depolarizer (17) that depolarizes each of the polarization components from the polarization-splitter (13), light receiving element that converts the two lights that were depolarized by the depolarizer (17) to a first signal (S1) and a second signal (S2) respectively, and a signal processing unit (15) that, based on the first signal (S1) and the second signal (S2), determines the magnitude of a Faraday rotation applied to the linearly-polarized light, and thereby calculates a value of the current to be measured.