The present invention relates to a magnetic sensor which can improve the detection precision of a weak magnetic field. A magnetic sensor wherein a magnetic body which changes the direction of a magnetic field input to a magnetoresistance effect element is provided in the vicinity of the magnetoresistance effect element in which the resistance value changes according to the direction of the input magnetic field, and the magnetic body has a recess with a concave shape on the surface at a side where the magnetoresistance effect element is formed. The center of the recess may be substantially identical to that of the magnetic body. The concave shape may at least include polygon having three or more sides, or may at least include arc.