An electric motor-driven sewing machine which includes a drive mechanism for driving the machine by an electric motor, a mechanism for stopping operation of the machine by a brake, an automatic thread trimmer mechanism, a wiper mechanism for removing the trimmed thread, command switches for providing command signals to the sewing machine and control circuit means for controlling the various operations of the sewing machine in accordance with electrical signals. Apparatus is provided for detecting an abnormal state in which input signals which are not to take place simultaneously occur simultaneously, and to invalidate the operations of the various mechanisms of the sewing machine to protect the user from danger due to erroneous operations of the sewing machine.