Control parameters such as an acceleration/deceleration time constant Tf, a position loop gain Kpf, a velocity loop proportional gain Pvf, and a velocity loop integral gain Ivf, each including respective values assigned to each of a plurality of different inertia values J0˜Jmax, are changed based on an inertia value Jx calculated by an inertia identifying unit and an adjusted control parameter calculated by an automatic control-parameter adjustment unit.