PURPOSE: To prevent the generation of shortage of a bobbin thread in the course of sewing by warning and displaying the shortage of the bobbin thread quantity of a bobbin in a sewing machine at the time point of selecting a pattern with respect to the necessary quantity of the bobbin thread which can form a seam of the pattern.

CONSTITUTION: When a desired pattern is selected by operating a pattern selecting means 6, a pattern stored in a pattern seam information storage means 9 is designated and displayed on a pattern display means 8, and also, by a program stored in a bobbin thread necessary quantity arithmetic program storage means 17, the bobbin thread necessary quantity required for the pattern is calculated and displayed on a bobbin thread necessary quantity display means 18. Subsequently, a bobbin thread quantity detecting means 21 operates and detects the bobbin thread quantity of an installed bobbin. Next, the detected bobbin thread quantity and the bobbin thread necessary quantity are compared, and in the case the detected bobbin thread quantity is insufficient, a warning display is executed in a voice. In such a manner, before sewing is started, the bobbin thread quantity of the bobbin can be confirmed, and it is not feared that the bobbin thread is snapped on the way of sewing.