A device for detecting the presence of objects in a vehicle's blind spot. The invention relates to a device for detecting the presence of objects in a vehicle's blind spot, where the objects contain at least one ferromagnetic material whereby they distort the earth's magnetic field. The device is mounted on a vehicle that has at least one blind spot. The detection device can detect the object located in the blind spot because it is provided with a unit for detecting the distortion of the earth's magnetic field caused by the object. Preferably it includes a logical circuit with neural nets for processing the signals received from the sensors.