A dynamic optimization method for speed data, for compensating for a speed data maximum value and a minimum resolution that can be specified by users without depending on a speed pattern preparation cycle. A dynamic optimizing method for speed data used for preparing a speed instruction pattern fed to a motor in a positioning device, wherein a speed pattern generator (1) that calculates a desired speed pattern when a moving instruction (2) such as a moving distance, speed, acceleration time and deceleration time is input is provided, and a speed pattern preparation cycle (3) can be specified by users without the possibility that speed data maximum value and a minimum resolution of speed data are modified.