A magnetic detection device of which an output can be completely switched over with an external magnetic field is formed in a small size. A detection circuit is formed by forming circuit elements such as an active element layer and interconnection layers on a substrate. An insulating layer is formed on the detection circuit, and a flat surface is formed on the resultant surface. A magnetic detection element that detects an external magnetic field by using a magneto-resistance effect and a fixed resistance element, which has the same electric resistance as the magnetic detection element but does not react to the external magnetic field, are formed on the flat surface. Electrode layers and a lead layer are formed on the flat surface, and the lead layer and the interconnection layer are electrically connected to each other via a bump penetrating the insulating layer. The magnetic detection element and the fixed resistance element are formed on the flat surface of the insulating layer, thereby forming a small magnetic detection device.