PURPOSE: To improve operability by attaching/detaching a memory card as needed while a power source is turned on by automatically setting the state of cutting an external input/output circuit when it is discriminated that an external pattern, namely, the pattern group of a non-attached memory card is selected.

CONSTITUTION: When a pattern selecting means 6 is operated while the power source is turned on, a pattern group discriminating means 20 discriminates whether the selected pattern is external data or incorporated pattern group data. In this case, when it is discriminated that the pattern is the incorporated pattern group data, the pattern data are read out of a storage means 7 by operating a pattern selection switch 6b while observing the display of a pattern display means 13, and X and Y motors are driven synchronously with the revolution of a sewing machine motor. On the other hand, when the discriminating means 20 discriminates that the pattern is external data, the signal circuit and power source supply of an external data input/output circuit 8 are temporarily cut off by operating an external input/output cutting circuit 11, the cut-off is recovered after the memory card is mounted, and the pattern group display data of the memory card 9 are displayed on the pattern display means 13.