An electric current sensor includes a core having a coupling portion formed by bending a part of a plate member, and one end portion and the other end portion of the plate member are disposed to oppose to each other through a constant magnetic gap on a side opposite from the coupling portion. The core has: a first tapered portion in which a width of the plate member continuously decreases from one end of the coupling portion adjacent to the one end portion to a distal end of the one end portion; and a second tapered portion in which the width of the plate member continuously decreases from an other end of the coupling portion adjacent to the other end portion to a distal end of the other end portion.