To always and minimally maintain an estimation error without using a speed sensor nor an acceleration sensor and to control positioning with high accuracy.

An optimum estimation sampling interval calculating table 16 outputs an optimum sampling interval m in accordance with an acceleration command value ar that is given from a command value generator 4. An adaptive sampling speed estimating part 17 calculates a speed estimation value Vd based on the interval m that is outputted from the table 16 and a position detection value Xd from a digital position sensor 3. An adder-subtracter 14 adds a speed command value Vr from the generator 4 as feed forward to an differential output through a subtracter 12 and a position feedback gain (Gp) 13 and also subtracts the value Vd. A speed feedback gain (Gv) 15 amplifies an output value of the adder-subtracter 14 and outputs it as an operation amount u to a motor 1.