u2267 k or not step s16 if vs vm is less than k the minimum rate of speed vm as the speed of the initial stitch data of the block step s17 is set on the contrary if vs vm is more the k a predetermined value 34 a 34 is added to the set speed vs of the immediately preceded stitch data thereby to set the calculated rate of speed as the speed of the block step s18 then the point at another one address from which another block is to be formed step s19 is newly set and the routine is returned to the step s12 in case there are no following n number of stitch data from the step s12 the operation is as follows setting there the minimum rate of speed of fig4 step s20 and setting the point at the next address step s21 and then confirming if the operation is finished or not step s22 if the operation is not finished the routine is returned to the step s12 in the above mentioned embodiment though amendment is not performed when the deceleration is more than a predetermined value such deceleration may be amended by vs a when vs vm u2267 k however in case of deceleration it is required that the deceleration will always reach the minimum rate of speed vm and this is desired to be achieved in each block namely if n 3 the set speed must reach vm at the third stitch without fail this may be realized by providing a brake as mentioned above according to the embodiments of the invention instead of deciding the vertical reciprocating speed of the needle per stitch data each of the stitch data in series is elected.