A current transducer having an open/closed structure of a penetration piece through which a measurement target line passes, includes: one pair of Hall devices, formed on both end gaps of an upper side portion, for sensing a current amount of the line to be measured; a feedback coil, arranged on an upper portion of the Hall devices, for canceling out a magnetic flux density of a magnet by inducing a current of a reverse direction to a current conducted in the measurement target line; a closed loop current sensing circuit for measuring a current flowing into the feedback coil; and a signal conversion circuit section for converting a current form of the measurement target line measured from the closed loop current sensing circuit into a direct current conversion signal relative to an effective value required from equipment connected to the current transducer, and outputting the direct current conversion signal.