The magnetic sensor can prevent an increase of a positional detection error of a subject/object even in the case of applying an external magnetic field with a magnetic field intensity exceeding a predetermined range. A magnetic sensor is equipped with a magnetoresistive effect element (MR element) 11 that can detect an external magnetic field and a soft magnetic body shield 12. The soft magnetic body shield(s) 12 are/is positioned above and/or below the MR element 11 in a side view, and the size of the MR element 11 is physically included within a perimeter of the soft magnetic body shield 12.