To provide a magnetic sensor which has a magnetic amplification structure for improving sensitivity, is small, has high sensitivity, and has favorable temperature characteristics and its manufacturing method.

A semiconductor thin film 11 having a magnetosensitive section 11a is provided on a substrate 10. Metallic electrodes 12 are provided on both ends of the magnetosensitive section 11a. A first base layer 14 is provided through a protective layer 13 on the front side in the vicinity of the magnetosensitive section 11a. A first magnetic body 17 having a magnetic amplification function is provided on the first base layer 14. A second base layer 15 is provided on the substrate 10 and on the back of the magnetosensitive section 11a. A second magnetic body 18 having a magnetic amplification function, in conjunction with the first magnetic body 17, is provided on the second base layer 15. A simple manufacturing process performing only magnetic body plating can provide the magnetic amplification structure, thereby achieving the magnetic sensor which is small, has high sensitivity, and has favorable temperature characteristics.