A magnetically inductive flowmeter having a pressure-resistant housing made of plastic, comprising a measuring unit with a measuring channel of rectangular cross-section which is flown through by the measurement fluid, a channel wall, two opposing magnet poles at the channel wall, an electromagnet with magnet coil and magnet core for generating a magnetic alternating field as well as two opposing measurement electrodes in the channel wall. The magnet poles are punched, bent and folded parts made of electric sheet metal in the form of an elongate strip with mutually distanced surface elements formed thereon. The elongate strip forms a double web after folding. The surface elements form magnet pole surfaces after bending. The double web and the magnet pole surfaces form the magnet pole. The double web is located on the rear side of the magnet pole.