To provide a small-sized magnetic sensor capable of achieving closed-loop control. A magnetic sensor includes: a sensor chip mounted on a surface of a substrate such that an element formation surface is perpendicular to the surface of the substrate or inclined by a predetermined angle with respect thereto; an external magnetic member mounted on the surface of the substrate and collecting a magnetic field to be detected in a magnetosensitive element; and a compensating coil wound around the external magnetic member. The compensating coil is thus wound around the external magnetic member, so that it is possible to cancel a magnetic field to be applied to the magnetosensitive element and to prevent the external magnetic member from being magnetically saturated.