A current sensor includes: a magneto electric conversion element; and a magnetic field concentrating core applying a magnetic field caused by a measurement object current to the magneto electric conversion element. A planar shape of the magnetic field concentrating core perpendicular to a current flowing direction is a ring shape with a gap. The magneto electric conversion element is arranged in the gap. A part of a conductor for flowing the current is surrounded by the magnetic field concentrating core. The magnetic field concentrating core includes two first magnetic members and at least one second magnetic member, which are stacked alternately in the current flowing direction. Parts of the two first magnetic members adjacent to each other via the one second magnetic member are opposed to each other through a clearance or an insulator.