Abstract: Disclosed is an apparatus for detecting magnetically conductive metals in a flow of material. The apparatus includes a metal casing open at both ends thereof and adopted to receive the material flow therethrough. Magnet bars are attached at two opposite inner walls of the casing in such a manner that, on one side, the north poles are directed inwards into the casing and the south poles are attached magnetically conductively to the casing, and on the other side the polarity of the magnetic bars is opposite, detector means being provided at the two remaining walls of the casing so as to detect the magnetic field at those positions. Finally, electronic circuit elements are connected to the detectors in order to convert the detected magnetic field variations into an observable form. The material flow may take place in a trough positioned within and extending through the casing.