PURPOSE: To provide the device for detecting the residual amount of the sewing machine with an automatic thread cutter capable of accurately detecting the residual amount of the lower thread.

CONSTITUTION: The sewing machine having lower thread cutting means cutting a lower thread 11 wound around a lower thread bobbin 12 by means of two knives at least one of which is made a movable knife is provided with a rotational amount detecting means 18 detecting the rotational amount of the lower thread bobbin 12 with the lower thread 11 wound and a control means 29 detecting the rotational amount of the lower thread bobbin 12 by the rotational amount detecting means 18 between the time when the movable knife starts to feed the lower thread and the time when the uniform motion of the knife is ended and sending the prescribed operation signal in the case when the rotational amount of the lower thread bobbin 12 detected by the rotational amount detecting means 18 becomes the set value.