A current sensor includes an annular magnetic core that includes a closed magnetic path including a void in a portion thereof, and a magnetic body for focusing flux of a magnetic field generated around a conductor that carries a measured current, and a magnetic detecting portion for detecting flux of a magnetic field generated in the void of the magnetic core. The magnetic core includes a plurality of pairs of stepped portions on a pair of opposing end surfaces that form the void, the stepped portions descending along a direction separating from the conductor.