Résumé dans la langue de publication, traduction non disponible A device for sensing magnetism comprises an oscillation circuit (18) and waveshape change sensing circuits (22, 24). The oscillation circuit (18) includes a parallel oscillation circuit (15) consisting of a magnetic sensor (11) having a core made of a ferromagnetic substance and a sensing coil (13) wound on the core and of a capacitive element (14) connected in parallel with the sensing coil (13). The oscillation circuit (18) further includes an amplifier (16) to which a resistor (17) is connected as a feedback circuit element. The oscillation circuit (18) excites the core (12) to the saturation region thereof by its oscillating current. The waveshape change sensing circuits (22, 24) sense the waveshape change of the output signal (a) of the oscillation circuit (18). The core (12) is excited to the saturation region thereof by the oscillation circuit (18) which uses the sensing coil (13) of the magnetic sensor (11) as a part of the parallel resonance circuit (15) and thereby, the device senses an external magnetic field (H) applied to the magnetic sensor (11) by the quantity of change of the waveshape of the output signal (a) of the oscillation circuit (18). Consequently, the circuit configuration can be simplified, and the reduction of the size and the cost of the whole device can be attained keeping the high measuring accuracy thereof. (see diagramm 1 page 0)