An electric current sensor includes a primary conductor through which an electric current to be measured flows, and at least one magnetic sensor. The magnetic sensor includes a first magnetic sensor area, the output sensitivity of which is decreased when a magnetic field is applied to include a magnetic field component in a first direction along a sensitivity variation axis, and a second magnetic sensor area, the output sensitivity of which is increased when the magnetic field is applied to include a magnetic field component in a second direction that is opposite to the first direction.