To perform embroidery by combining and editing the patterns from different external memory devices even with a sewing machine with which the erasure of data occurs when a power source is switched off in order to replace the external memory devices.

Backup circuits which impress the voltage Vbkup capable of holding the data even if the power source is switched off are installed to a built-in VRAM 58 and RAM 54 which are inputted with the data for display for displaying the patterns on a screen and store the data of the computer sewing machine for embroidery sewing which requires the switching off of the power source at the time of exchange of the external memory device and with which the data stored in the built-in memory before the switching off of the power source is erased when the power source is switched off. At the time of exchange of the external memory device, before the switching off of the power source, the manipulation to store the saved information in the RAM 54 is carried out in such a manner that the data for display is held in the VRAM 58 by the backup circuit even if the power source is switched off, by which the formation of the combined patterns by combining the fresh patterns inputted from the different external memory device after the exchange is made possible.