In a synchronization operation instruction of a synchronization control of moving a slave axis at a certain ratio with respect to a master axis movement amount, a master axis movement amount before start of change of a synchronization magnification, used in an operation based on a synchronization magnification changing instruction, is determined by referring to a parameter of the synchronization operation instruction so that the operation based on the synchronization magnification changing instruction ends at a set synchronization start master axis position. With such a configuration, the synchronization control is started based on the synchronization operation instruction from the synchronization start master axis position set in the synchronization operation instruction.