A sewing machine is provided with a faulty-stitch detecting device (21) which is disposed between a thread take-up lever (16) and the needle. It comprises an eye (26) which guides the needle thread (17) and is deflectable substantially crosswise of the principal direction (33) of the needle thread (17). The deflections of the eye (26) lead to changes of a magnetic field that is produced by a magnet (32) and are detected by a sensor (36) and converted into control signals of the sewing machine. (FIG.2)