To achieve a compact configuration and a high integration for a magnetic sensor.

This amorphous magnetic sensor imparts the adequate operating point to the magnetic body by flowing the stabilized optimum AC alternating current to an amorphous core (a) itself directly, directly performs amplification and synchronous rectification (phase detection, sample holding and the like) from a stable resistor (detecting resistor) (c) for the phaseshifting magnetic signal generated in the core (a), the magnetic signal induced in a sense coil (f) wound around the core or the signal waveform generated in the core and obtains the magnetic output. Therefore, in this constitution, the magnetic sensor having the stable operation can be made compact or can be made to be the integrated circuit.