In a position control device based on a current observer control for performing two degree of freedom control, deterioration of the position accuracy caused by the output delay due to computation is prevented. In the two degree of freedom control system for preventing overrun, the delay of output of the two degree of freedom control (computing delay and hardware delay of drive amplifier, D/A converter, etc.) is considered, and the estimated state of Td which is advanced by the amount of delay from the sample point of time is computed, then output is computed based on this estimated state. So even if state changes during calculation from the sample point of time, the influence of the output delay can be prevented, and highly accurate position control can be performed, therefore overrun can be prevented.