PURPOSE: To selectively set a machining speed and a communication baud rate matching the performance of an NC device.

CONSTITUTION: A distribution table of movement quantities commanded to respective blocks by an NC program is generated (S2). A permissible command speed Vn is calculated from a set maximum command speed for each movement quantity in the distribution table and stored in the distribution table (S3). It is judged whether or not movement commands can be outputted, cycle by cycle, to a servo system at commands speeds commanded by programs by blocks without any break (S4). When a command speed is too fast to make a break, a program is registered instead of a proper speed stored in the distribution table (S5, S6, and S7). When a sign 'OK' is given to a proper speed in the distribution table and a sign 'NG' is given to an improper speed; and the speeds are displayed (S8). For the communication baud rate, a proper baud rate is found from the number of character data of the blocks and the distribution table of movement quantities and when a set baud rate is low, extension is indicated.